Light-emitting device comprising transparent conductive films having different thicknesses

ABSTRACT

A light-emitting device includes a first light-emitting element emitting blue light, a second light-emitting element emitting green light, and a third light-emitting element emitting red light. A first reflective electrode and a first transparent conductive film, a second reflective electrode and a second transparent conductive film, and a third reflective electrode and a third transparent conductive film are stacked in the first to third light-emitting elements, respectively. A first light-emitting layer, a charge-generation layer, a second light-emitting layer, and an electrode are stacked in this order over each of the first transparent conductive film, the second transparent conductive film, and the third transparent conductive film. The electrode has functions of transmitting and reflecting light. The first to third reflective electrodes contain silver. The first transparent conductive film is thicker than the third transparent conductive film. The third transparent conductive film is thicker than the second transparent conductive film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/710,115, filed May 12, 2015, now allowed, which claims the benefit ofa foreign priority application filed in Japan as Serial No. 2014-101116on May 15, 2014, both of which are incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

One embodiment of the present invention relates to a light-emittingelement in which a light-emitting layer capable of providing lightemission by application of an electric field is provided between a pairof electrodes, and also relates to a light-emitting device, anelectronic device, and a lighting device each including such alight-emitting element.

Note that one embodiment of the present invention is not limited to theabove technical field. The technical field of one embodiment of theinvention disclosed in this specification and the like relates to anobject, a method, or a manufacturing method. In addition, one embodimentof the present invention relates to a process, a machine, manufacture,or a composition of matter. Specifically, examples of the technicalfield of one embodiment of the present invention disclosed in thisspecification include a semiconductor device, a display device, a liquidcrystal display device, a light-emitting device, a lighting device, apower storage device, a storage device, a driving method thereof, and amanufacturing method thereof.

2. Description of the Related Art

In recent years, research and development have been extensivelyconducted on light-emitting elements utilizing electroluminescence (EL).In a basic structure of these light-emitting elements, a layercontaining a light-emitting substance is provided between a pair ofelectrodes. By application of a voltage to this element, light emissionfrom the light-emitting substance can be obtained.

Since the above light-emitting element is a self-luminous type, alight-emitting device using this light-emitting element has advantagessuch as high visibility, no necessity of a backlight, and low powerconsumption. The light-emitting device using the light-emitting elementalso has advantages in that it can be manufactured to be thin andlightweight and has high response speed.

In order to improve the extraction efficiency of light from alight-emitting element, a method has been proposed, in which a microoptical resonator (microcavity) structure utilizing a resonant effect oflight between a pair of electrodes is used to increase the intensity oflight having a specific wavelength (e.g., see Patent Document 1).

REFERENCE

[Patent Document]

-   [Patent Document 1] Japanese Published Patent Application No.    2012-182127

SUMMARY OF THE INVENTION

When a metal film with high reflectivity (e.g., a metal film containingsilver) is used as one of a pair of electrodes in a micro opticalresonator structure (hereinafter referred to as a microcavity structure)utilizing a resonant effect of light between the pair of electrodes,light might be scattered or absorbed in the vicinity of a surface of themetal film with high reflectivity under the influence of surface plasmonresonance (SPR), resulting in a lower light extraction efficiency.

In view of the above problems, an object of one embodiment of thepresent invention is to provide a novel light-emitting device. Anotherobject is to provide a novel light-emitting device with a high emissionefficiency and a low power consumption. Another object is to provide amethod for manufacturing the novel light-emitting device.

Note that the description of the above objects does not disturb theexistence of other objects. In one embodiment of the present invention,there is no need to achieve all the objects. Other objects will beapparent and can be derived from the description of the specificationand the like.

One embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element that emits blue light, a secondlight-emitting element that emits green light, and a thirdlight-emitting element that emits red light. In the first light-emittingelement, a first reflective electrode, a first transparent conductivefilm, a first light-emitting layer, a charge-generation layer, a secondlight-emitting layer, and an electrode are stacked in this order. In thesecond light-emitting element, a second reflective electrode, a secondtransparent conductive film, the first light-emitting layer, thecharge-generation layer, the second light-emitting layer, and theelectrode are stacked in this order. In the third light-emittingelement, a third reflective electrode, a third transparent conductivefilm, the first light-emitting layer, the charge-generation layer, thesecond light-emitting layer, and the electrode are stacked in thisorder. The electrode has a function of transmitting light and a functionof reflecting light. The first to third reflective electrodes eachcontain silver. The first transparent conductive film is thicker thanthe third transparent conductive film, and the third transparentconductive film is thicker than the second transparent conductive film.Details of the light-emitting device are described below.

One embodiment of the present invention is a light-emitting deviceemitting lights of a plurality of colors, which includes a firstlight-emitting element having a function of emitting blue light, asecond light-emitting element having a function of emitting green light,and a third light-emitting element having a function of emitting redlight. The first light-emitting element includes a first reflectiveelectrode, a first transparent conductive film over the first reflectiveelectrode, a first light-emitting layer over the first transparentconductive film, a charge-generation layer over the first light-emittinglayer, a second light-emitting layer over the charge-generation layer,and an electrode over the second light-emitting layer. The secondlight-emitting element includes a second reflective electrode, a secondtransparent conductive film over the second reflective electrode, thefirst light-emitting layer over the second transparent conductive film,the charge-generation layer over the first light-emitting layer, thesecond light-emitting layer over the charge-generation layer, and theelectrode over the second light-emitting layer. The third light-emittingelement includes a third reflective electrode, a third transparentconductive film over the third reflective electrode, the firstlight-emitting layer over the third transparent conductive film, thecharge-generation layer over the first light-emitting layer, the secondlight-emitting layer over the charge-generation layer, and the electrodeover the second light-emitting layer. The electrode has a function oftransmitting light and a function of reflecting light. The first tothird reflective electrodes each contain silver. The first transparentconductive film has a first region, the second transparent conductivefilm has a second region, and the third transparent conductive film hasa third region. The first region is thicker than the third region, andthe third region is thicker than the second region.

In the above structure, preferably, the first light-emitting layercontains a first light-emitting substance that emits light of at leastone of violet, blue, and blue green, and the second light-emitting layercontains a second light-emitting substance that emits light of at leastone of green, yellow green, yellow, orange, and red. In that case,preferably, the optical path length between the first reflectiveelectrode and the first light-emitting layer is greater than or equal to¾λ_(B). In addition, preferably, the optical path length between thesecond reflective electrode and the first light-emitting layer is lessthan ¾λ_(G), and the optical path length between the third reflectiveelectrode and the first light-emitting layer is less than ¾λ_(R).

In each of the above structures, preferably, the optical path lengthbetween the second reflective electrode and the second light-emittinglayer is around ¾λ_(G), and the optical path length between the thirdreflective electrode and the second light-emitting layer is around¾λ_(R).

Another embodiment of the present invention is a light-emitting deviceemitting lights of a plurality of colors, which includes a firstlight-emitting element having a function of emitting blue light, asecond light-emitting element having a function of emitting green light,a third light-emitting element having a function of emitting red light,and a fourth light-emitting element having a function of emitting yellowlight. The first light-emitting element includes a first reflectiveelectrode, a first transparent conductive film over the first reflectiveelectrode, a first light-emitting layer over the first transparentconductive film, a charge-generation layer over the first light-emittinglayer, a second light-emitting layer over the charge-generation layer,and an electrode over the second light-emitting layer. The secondlight-emitting element includes a second reflective electrode, a secondtransparent conductive film over the second reflective electrode, thefirst light-emitting layer over the second transparent conductive film,the charge-generation layer over the first light-emitting layer, thesecond light-emitting layer over the charge-generation layer, and theelectrode over the second light-emitting layer. The third light-emittingelement includes a third reflective electrode, a third transparentconductive film over the third reflective electrode, the firstlight-emitting layer over the third transparent conductive film, thecharge-generation layer over the first light-emitting layer, the secondlight-emitting layer over the charge-generation layer, and the electrodeover the second light-emitting layer. The fourth light-emitting elementincludes a fourth reflective electrode, a fourth transparent conductivefilm over the fourth reflective electrode, the first light-emittinglayer over the fourth transparent conductive film, the charge-generationlayer over the first light-emitting layer, the second light-emittinglayer over the charge-generation layer, and the electrode over thesecond light-emitting layer. The electrode has a function oftransmitting light and a function of reflecting light. The first tofourth electrodes each contain silver. The first transparent conductivefilm has a first region, the second transparent conductive film has asecond region, the third transparent conductive film has a third region,and the fourth transparent conductive film has a fourth region. Thefirst region is thicker than the third region, the third region isthicker than the fourth region, and the fourth region is thicker thanthe second region.

In the above structure, preferably, the first light-emitting layercontains a first light-emitting substance that emits blue light, and thesecond light-emitting layer contains a second light-emitting substancethat emits light of at least one of green, yellow, and red. In thatcase, preferably, the optical path length between the first reflectiveelectrode and the first light-emitting layer is greater than or equal to¾λ₈. In addition, preferably, the optical path length between the secondreflective electrode and the first light-emitting layer is less than¾λ_(G), the optical path length between the third reflective electrodeand the first light-emitting layer is less than ¾λ_(R), and the opticalpath length between the fourth reflective electrode and the firstlight-emitting layer is less than ¾λ_(Y).

In each of the above structures, preferably, the optical path lengthbetween the second reflective electrode and the second light-emittinglayer is around ¾λ_(G), the optical path length between the thirdreflective electrode and the second light-emitting layer is around ¾λ_(R), and the optical path length between the fourth reflectiveelectrode and the second light-emitting layer is around ¾λ_(Y).

In each of the above structures, preferably, a first optical elementoverlapping with the first light-emitting element, a second opticalelement overlapping with the second light-emitting element, and a thirdoptical element overlapping with the third light-emitting element areprovided; the first optical element has a function of transmitting bluelight, the second optical element has a function of transmitting greenlight, and the third optical element has a function of transmitting redlight.

One embodiment of the present invention also includes, in its category,an electronic device including the light-emitting device with any of theabove structures and a housing or a touch sensor, or a lighting deviceincluding the light-emitting device with any of the above structures anda housing or a touch sensor. In addition, a light-emitting device inthis specification refers to an image display device or a light source(including a lighting device). Furthermore, a light-emitting deviceincludes, in its category, all of a module in which a light-emittingdevice is connected to a connector such as a flexible printed circuit(FPC) or a tape carrier package (TCP), a module in which a printedwiring board is provided on the tip of a TCP, and a module in which anintegrated circuit (IC) is directly mounted on a light-emitting elementby a chip on glass (COG) method.

According to one embodiment of the present invention, a novellight-emitting device can be provided. According to another embodimentof the present invention, a novel light-emitting device with a highemission efficiency and a low power consumption can be provided.According to another embodiment of the present invention, a method formanufacturing the novel light-emitting device can be provided.

Note that the description of these effects does not disturb theexistence of other effects. One embodiment of the present invention doesnot necessarily achieve all the effects listed above. Other effects willbe apparent and can be derived from the description of thespecification, the drawings, the claims, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are cross-sectional views each illustrating alight-emitting device according to one embodiment of the presentinvention.

FIGS. 2A and 2B are cross-sectional views each illustrating alight-emitting device according to one embodiment of the presentinvention.

FIG. 3 is a cross-sectional view illustrating a light-emitting deviceaccording to one embodiment of the present invention.

FIGS. 4A and 4B are cross-sectional views each illustrating alight-emitting device according to one embodiment of the presentinvention.

FIG. 5 is a cross-sectional view illustrating a light-emitting deviceaccording to one embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a light-emitting deviceaccording to one embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a light-emitting deviceaccording to one embodiment of the present invention.

FIGS. 8A to 8D are cross-sectional views illustrating a method formanufacturing a light-emitting device according to one embodiment of thepresent invention.

FIGS. 9A and 9B are cross-sectional views illustrating a method formanufacturing a light-emitting device according to one embodiment of thepresent invention.

FIGS. 10A and 10B are a top view and a cross-sectional view illustratinga display device according to one embodiment of the present invention.

FIGS. 11A and 11B are a block diagram and a circuit diagram illustratinga display device according to one embodiment of the present invention.

FIG. 12 is a perspective view illustrating a display module.

FIGS. 13A to 13G illustrate electronic devices.

FIG. 14 illustrates lighting devices.

FIG. 15 illustrates an element structure used in Examples.

FIGS. 16A and 16B are graphs showing current efficiency-luminancecharacteristics and current-voltage characteristics of light-emittingelements fabricated in Example 1.

FIG. 17 is a graph showing luminance-voltage characteristics oflight-emitting elements fabricated in Example 1.

FIG. 18 is a graph showing emission spectra of light-emitting elementsfabricated in Example 1.

FIGS. 19A and 19B are graphs showing current efficiency-luminancecharacteristics and current-voltage characteristics of light-emittingelements fabricated in Example 2.

FIG. 20 is a graph showing luminance-voltage characteristics oflight-emitting elements fabricated in Example 2.

FIG. 21 is a graph showing emission spectra of light-emitting elementsfabricated in Example 2.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described in detail belowwith reference to the drawings. Note that the present invention is notlimited to the following description, and the modes and details thereofcan be modified in various ways without departing from the spirit andscope of the present invention. Accordingly, the present inventionshould not be interpreted as being limited to the content of theembodiments below.

Note that the position, the size, the range, or the like of eachstructure illustrated in drawings and the like is not accuratelyrepresented in some cases for easy understanding. Therefore, thedisclosed invention is not necessarily limited to the position, thesize, the range, or the like disclosed in the drawings and the like.

The ordinal numbers such as “first” and “second” in this specificationand the like are used for convenience and do not denote the order ofsteps or the stacking order of layers. Therefore, for example,description can be made even when “first” is replaced with “second” or“third”, as appropriate. In addition, the ordinal numbers in thisspecification and the like are not necessarily the same as those whichspecify one embodiment of the present invention.

In order to describe structures of the invention with reference to thedrawings in this specification and the like, the same reference numeralsare used in common for the same portions in different drawings.

In this specification and the like, blue light has at least one peak ofemission spectrum in the wavelength range of greater than or equal to420 nm and less than or equal to 480 nm, green light has at least onepeak of emission spectrum in the wavelength range of greater than orequal to 500 nm and less than 550 nm, yellow light has at least one peakof emission spectrum in the wavelength range of greater than or equal to550 nm and less than or equal to 580 nm, and red light has at least onepeak of emission spectrum in the wavelength range of greater than orequal to 600 nm and less than or equal to 740 nm.

In this specification and the like, a transparent conductive filmtransmits visible light and has conductivity. Examples of thetransparent conductive film include an oxide conductor film typified byan indium tin oxide (ITO) film, an oxide semiconductor film, and anorganic conductive film containing an organic substance. Examples of theorganic conductive film containing an organic substance include a filmcontaining a composite material in which an organic compound and anelectron donor (donor) are mixed and a film containing a compositematerial in which an organic compound and an electron acceptor(acceptor) are mixed. The resistivity of the transparent conductive filmis preferably lower than or equal to 1×10⁵ Ω·cm, more preferably lowerthan or equal to 1×10⁴ Ω·cm.

In this specification and the like, the terms “film” and “layer” can beinterchanged with each other depending on the case or circumstances. Forexample, the term “conductive layer” can be changed into the term“conductive film” in some cases. Also, the term “insulating film” can bechanged into the term “insulating layer” in some cases.

Embodiment 1

In this embodiment, a light-emitting device according to one embodimentof the present invention and a method for manufacturing thelight-emitting device will be described below with reference to FIGS. 1Aand 1B, FIGS. 2A and 2B, FIG. 3, FIGS. 4A and 4B, FIG. 5, FIG. 6, FIG.7, FIGS. 8A to 8D, and FIGS. 9A and 9B.

Structural Example 1 of Light-Emitting Device

FIG. 1A is a cross-sectional view illustrating an example of alight-emitting device according to one embodiment of the presentinvention. A light-emitting device 100 illustrated in FIG. 1A includes afirst light-emitting element 101B having a function of emitting bluelight, a second light-emitting element 101G having a function ofemitting green light, and a third light-emitting element 101R having afunction of emitting red light.

The first light-emitting element 101B includes a first reflectiveelectrode 104B, a first transparent conductive film 106B over the firstreflective electrode 104B, a first light-emitting layer 108 over thefirst transparent conductive film 106B, a charge-generation layer 110over the first light-emitting layer 108, a second light-emitting layer112 over the charge-generation layer 110, and a semi-transmissive andsemi-reflective electrode 114 over the second light-emitting layer 112.The second light-emitting element 101G includes a second reflectiveelectrode 104G, a second transparent conductive film 106G over thesecond reflective electrode 104G, the first light-emitting layer 108over the second transparent conductive film 106G, the charge-generationlayer 110 over the first light-emitting layer 108, the secondlight-emitting layer 112 over the charge-generation layer 110, and thesemi-transmissive and semi-reflective electrode 114 over the secondlight-emitting layer 112. The third light-emitting element 101R includesa third reflective electrode 104R, a third transparent conductive film106R over the third reflective electrode 104R, the first light-emittinglayer 108 over the third transparent conductive film 106R, thecharge-generation layer 110 over the first light-emitting layer 108, thesecond light-emitting layer 112 over the charge-generation layer 110,and the semi-transmissive and semi-reflective electrode 114 over thesecond light-emitting layer 112. Note that the semi-transmissive andsemi-reflective electrode 114 is simply referred to as an electrode insome cases.

The first reflective electrode 104B, the second reflective electrode104G, and the third reflective electrode 104R each contain silver. Whenthe first reflective electrode 104B, the second reflective electrode104G, and the third reflective electrode 104R are each formed using amaterial containing silver, the reflectivity can be increased and theemission efficiency of each light-emitting element can be increased. Forexample, a conductive film containing silver is formed and separatedinto an island-shape; in this way, the first reflective electrode 104B,the second reflective electrode 104G, and the third reflective electrode104R can be formed. The first reflective electrode 104B, the secondreflective electrode 104G, and the third reflective electrode 104R arepreferably formed through a step of processing the same conductive film,because the manufacturing cost can be reduced.

In FIG. 1A, the second light-emitting layer 112 includes a secondlight-emitting layer 112 a and a second light-emitting layer 112 b. Thesecond light-emitting layer 112 can have a single-layer structure, astacked structure including two layers as illustrated in FIG. 1A, or astacked structure including three or more layers.

The first light-emitting layer 108 contains a first light-emittingsubstance that emits light of at least one of violet, blue, and bluegreen, and the second light-emitting layer 112 contains a secondlight-emitting substance that emits light of at least one of green,yellow green, yellow, orange, and red. When the second light-emittinglayer 112 has a stacked structure, the second light-emitting layer 112may contain light-emitting substances that emit lights of differentcolors or light-emitting substances that emit light of the same color.For example, a light-emitting substance that emits green light can beused for the second light-emitting layer 112 a, and a light-emittingsubstance that emits red light can be used for the second light-emittinglayer 112 b. Alternatively, light-emitting substances that emit yellowlight can be used for both the second light-emitting layers 112 a and112 b.

In such a manner, in the light-emitting device 100, the firstlight-emitting substance contained in the first light-emitting layer 108and the second light-emitting substance contained in the secondlight-emitting layer 112 are selected so that a desired emissionwavelength can be amplified, whereby light close to monochromatic lightcan be obtained. Also, in the light-emitting device 100, light emissionfrom the first light-emitting substance contained in the firstlight-emitting layer 108 and light emission from the secondlight-emitting substance contained in the second light-emitting layer112 can be combined so that white light emission can be obtained.

In FIG. 1A, blue light (B), green light (G), and red light (R) emittedfrom their respective light-emitting elements are schematically denotedby arrows of dashed lines. The same applies to light-emitting devicesdescribed later. The light-emitting device 100 illustrated in FIG. 1Ahas a top-emission structure in which light emitted from light-emittingelements is extracted to the side opposite to the substrate 102 sidewhere the light-emitting elements are formed. However, one embodiment ofthe present invention is not limited thereto and may have abottom-emission structure as illustrated in FIG. 2A in which lightemitted from light-emitting elements is extracted to the substrate 102side where the light-emitting elements are formed, or a dual-emissionstructure as illustrated in FIG. 2B in which light emitted fromlight-emitting elements is extracted in both top and bottom directionsof the substrate 102 where the light-emitting elements are formed.

In FIG. 1A, the first light-emitting layer 108, the charge-generationlayer 110, the second light-emitting layer 112, and thesemi-transmissive and semi-reflective electrode 114 are separated forthe first to third light-emitting elements 101B to 101R; however, theycan also be used without being separated. Therefore, in the secondlight-emitting element 101G and the third light-emitting element 101R,the first light-emitting layer 108, the charge-generation layer 110, thesecond light-emitting layer 112, and the semi-transmissive andsemi-reflective electrode 114 are represented by the same hatchingpatterns as in the first light-emitting element 101B and not especiallydenoted by reference numerals.

The first light-emitting element 101B, the second light-emitting element101G, and the third light-emitting element 101R each have a microcavitystructure. The microcavity structure of each light-emitting element willbe described below.

Light emitted from the first light-emitting layer 108 and the secondlight-emitting layer 112 resonates between a pair of electrodes (betweenthe first reflective electrode 104B and the semi-transmissive andsemi-reflective electrode 114, between the second reflective electrode104G and the semi-transmissive and semi-reflective electrode 114, andbetween the third reflective electrode 104R and the semi-transmissiveand semi-reflective electrode 114). In the light-emitting device 100,the thickness of each of the first transparent conductive film 106B, thesecond transparent conductive film 106G, and the third transparentconductive film 106R in the light-emitting elements is adjusted so thata desired wavelength of light emitted from the first light-emittinglayer 108 and the second light-emitting layer 112 can be amplified.

Specifically, the thickness of the first transparent conductive film106B is adjusted so that the optical path length between the firstreflective electrode 104B and the semi-transmissive and semi-reflectiveelectrode 114 can be m_(x)λ_(B)/2 (m_(x) is a natural number and λ_(B)is a wavelength (greater than or equal to 420 nm and less than or equalto 480 nm) of blue light). In addition, the thickness of the secondtransparent conductive film 106G is adjusted so that the optical pathlength between the second reflective electrode 104G and thesemi-transmissive and semi-reflective electrode 114 can be m_(y)λ_(G)/2(m_(y) is a natural number and λ_(G) is a wavelength (greater than orequal to 500 nm and less than 550 nm) of green light). In addition, thethickness of the third transparent conductive film 106R is adjusted sothat the optical path length between the third reflective electrode 104Rand the semi-transmissive and semi-reflective electrode 114 can bem_(z)λ_(R)/2 (m_(z) is a natural number and λ_(R) is a wavelength(greater than or equal to 600 nm and less than or equal to 740 nm) ofred light).

By adjusting the thickness of the first transparent conductive film106B, the optical path length between the first reflective electrode104B and the first light-emitting layer 108 is set to greater than orequal to ¾λ_(B), preferably greater than or equal to ¾λ_(B) and lessthan or equal to 5/4λ_(B). For example, when the optical path lengthbetween the first reflective electrode 104B and the first light-emittinglayer 108 is around ¼λ_(B), light is scattered or absorbed in thevicinity of a surface of the first reflective electrode 104B, resultingin a lower light extraction efficiency. However, in the light-emittingdevice 100, the optical path length between the first reflectiveelectrode 104B and the first light-emitting layer 108 is set to greaterthan or equal to ¾λ_(B), preferably greater than or equal to ¾λ_(B) andless than or equal to 5/4λ_(B), whereby scattering or absorption oflight in the vicinity of the surface of the first reflective electrode104B can be suppressed and thus a high light extraction efficiency canbe achieved. Accordingly, in the first light-emitting element 101B, bluelight can be efficiently extracted from the first light-emittingsubstance contained in the first light-emitting layer 108.

By adjusting the thickness of the second transparent conductive film106G, the optical path length between the second reflective electrode104G and the first light-emitting layer 108 can be less than ¾ λ_(G),preferably greater than or equal to ¼λ_(G) and less than ¾λ_(G). Byadjusting the thickness of the second transparent conductive film 106G,the optical path length between the second reflective electrode 104G andthe second light-emitting layer 112 can be around ¾λ_(G). By adjustingthe thickness of the third transparent conductive film 106R, the opticalpath length between the third reflective electrode 104R and the firstlight-emitting layer 108 can be less than ¾λ_(R), preferably greaterthan or equal to ¼λ_(R) and less than ¾λ_(R). By adjusting the thicknessof the third transparent conductive film 106R, the optical path lengthbetween the third reflective electrode 104R and the secondlight-emitting layer 112 can be around ¾λ_(R). When the optical pathlength is set as described above, green light can be efficientlyextracted from the second light-emitting substance contained in thesecond light-emitting layer 112 in the second light-emitting element101G, and red light can be efficiently extracted from the secondlight-emitting substance contained in the second light-emitting layer112 in the third light-emitting element 101R.

As described above, the first transparent conductive film 106B, thesecond transparent conductive film 106G, and the third transparentconductive film 106R each have a function of adjusting the optical pathlength in each light-emitting element. When the optical path length isadjusted in each light-emitting element, the first transparentconductive film 106B is formed to be thicker than the third transparentconductive film 106R, and the third transparent conductive film 106R isformed to be thicker than the second transparent conductive film 106G.In other words, the first transparent conductive film 106B has a firstregion, the second transparent conductive film 106G has a second region,and the third transparent conductive film 106R has a third region; thefirst region is thicker than the third region, and the third region isthicker than the second region.

The optical path length between the first reflective electrode 104B andthe semi-transmissive and semi-reflective electrode 114 is, to be exact,represented by the product of a refractive index and the thickness froma reflective region in the first reflective electrode 104B to areflective region in the semi-transmissive and semi-reflective electrode114. However, it is difficult to precisely determine the positions ofthe reflective regions in the first reflective electrode 104B and thesemi-transmissive and semi-reflective electrode 114; therefore, it isassumed that the above effect can be sufficiently obtained with thereflective regions set in given positions in the first reflectiveelectrode 104B and the semi-transmissive and semi-reflective electrode114. The same applies to the optical path length between the secondreflective electrode 104G and the semi-transmissive and semi-reflectiveelectrode 114 and the optical path length between the third reflectiveelectrode 104R and the semi-transmissive and semi-reflective electrode114.

Furthermore, the optical path length between the first reflectiveelectrode 104B and the light-emitting layer emitting desired light is,to be exact, the optical path length between the reflective region inthe first reflective electrode 104B and a light-emitting region in thelight-emitting layer emitting desired light. However, it is difficult toexactly determine the positions of the reflective region in the firstreflective electrode 104B and the light-emitting region in thelight-emitting layer emitting desired light; therefore, it is assumedthat the above effect can be sufficiently obtained with the reflectiveregion and the light-emitting region set in given positions in the firstreflective electrode 104B and the light-emitting layer emitting desiredlight. The same applies to the optical path length between the secondreflective electrode 104G and the light-emitting layer emitting desiredlight and the optical path length between the third reflective electrode104R and the light-emitting layer emitting desired light.

As described above, in the light-emitting device 100 illustrated in FIG.1A, the optical path length between the reflective electrode (the firstreflective electrode 104B, the second reflective electrode 104G, or thethird reflective electrode 104R) and the semi-transmissive andsemi-reflective electrode 114 of each light-emitting element isadjusted, whereby scattering or absorption of light in the vicinity ofthe surface of the reflective electrode can be suppressed and thus ahigh light extraction efficiency can be achieved. Therefore, a novellight-emitting device with a high emission efficiency and a low powerconsumption can be provided.

Structural Example 2 of Light-Emitting Device

Next, a structural example different from that of the light-emittingdevice 100 illustrated in FIG. 1A will be described below with referenceto FIG. 1B.

FIG. 1B is a cross-sectional view illustrating an example of alight-emitting device according to one embodiment of the presentinvention. In FIG. 1B, a portion having a function similar to that inFIG. 1A is represented by the same hatch pattern as in FIG. 1A and notespecially denoted by a reference numeral in some cases. In addition,common reference numerals are used for portions having similarfunctions, and a detailed description of the portions is omitted in somecases.

A light-emitting device 100A illustrated in FIG. 1B includes the firstlight-emitting element 101B having a function of emitting blue light,the second light-emitting element 101G having a function of emittinggreen light, and the third light-emitting element 101R having a functionof emitting red light.

The first light-emitting element 101B includes the first reflectiveelectrode 104B, the first transparent conductive film 106B over thefirst reflective electrode 104B, a first hole-injection layer 131 overthe first transparent conductive film 106B, a first hole-transport layer132 over the first hole-injection layer 131, the first light-emittinglayer 108 over the first hole-transport layer 132, a firstelectron-transport layer 133 over the first light-emitting layer 108, afirst electron-injection layer 134 over the first electron-transportlayer 133, the charge-generation layer 110 over the firstelectron-injection layer 134, a second hole-injection layer 135 over thecharge-generation layer 110, a second hole-transport layer 136 over thesecond hole-injection layer 135, the second light-emitting layer 112over the second hole-transport layer 136, a second electron-transportlayer 137 over the second light-emitting layer 112, a secondelectron-injection layer 138 over the second electron-transport layer137, and the semi-transmissive and semi-reflective electrode 114 overthe second electron-injection layer 138.

The second light-emitting element 101G includes the second reflectiveelectrode 104G, the second transparent conductive film 106G over thesecond reflective electrode 104G, the first hole-injection layer 131over the second transparent conductive film 106G, the firsthole-transport layer 132 over the first hole-injection layer 131, thefirst light-emitting layer 108 over the first hole-transport layer 132,the first electron-transport layer 133 over the first light-emittinglayer 108, the first electron-injection layer 134 over the firstelectron-transport layer 133, the charge-generation layer 110 over thefirst electron-injection layer 134, the second hole-injection layer 135over the charge-generation layer 110, the second hole-transport layer136 over the second hole-injection layer 135, the second light-emittinglayer 112 over the second hole-transport layer 136, the secondelectron-transport layer 137 over the second light-emitting layer 112,the second electron-injection layer 138 over the secondelectron-transport layer 137, and the semi-transmissive andsemi-reflective electrode 114 over the second electron-injection layer138.

The third light-emitting element 101R includes the third reflectiveelectrode 104R, the third transparent conductive film 106R over thethird reflective electrode 104R, the first hole-injection layer 131 overthe third transparent conductive film 106R, the first hole-transportlayer 132 over the first hole-injection layer 131, the firstlight-emitting layer 108 over the first hole-transport layer 132, thefirst electron-transport layer 133 over the first light-emitting layer108, the first electron-injection layer 134 over the firstelectron-transport layer 133, the charge-generation layer 110 over thefirst electron-injection layer 134, the second hole-injection layer 135over the charge-generation layer 110, the second hole-transport layer136 over the second hole-injection layer 135, the second light-emittinglayer 112 over the second hole-transport layer 136, the secondelectron-transport layer 137 over the second light-emitting layer 112,the second electron-injection layer 138 over the secondelectron-transport layer 137, and the semi-transmissive andsemi-reflective electrode 114 over the second electron-injection layer138.

As described above, in the light-emitting device 100A, the followingcomponents are provided in addition to the components of thelight-emitting device 100: the first hole-injection layer 131 and thefirst hole-transport layer 132 between the transparent conductive films(the first transparent conductive film 106B, the second transparentconductive film 106G, and the third transparent conductive film 106R)and the first light-emitting layer 108, the first electron-transportlayer 133 and the first electron-injection layer 134 between the firstlight-emitting layer 108 and the charge-generation layer 110, the secondhole-injection layer 135 and the second hole-transport layer 136 betweenthe charge-generation layer 110 and the second light-emitting layer 112,and the second electron-transport layer 137 and the secondelectron-injection layer 138 between the second light-emitting layer 112and the semi-transmissive and semi-reflective electrode 114.

In the light-emitting device 100A, the optical path length between thefirst reflective electrode 104B and the first light-emitting layer 108is adjusted with the thickness of at least one of the first transparentconductive film 106B, the first hole-injection layer 131, and the firsthole-transport layer 132; the optical path length between the secondreflective electrode 104G and the first light-emitting layer 108 isadjusted with the thickness of at least one of the second transparentconductive film 106G, the first hole-injection layer 131, and the firsthole-transport layer 132; and the optical path length between the thirdreflective electrode 104R and the first light-emitting layer 108 isadjusted with the thickness of at least one of the third transparentconductive film 106R, the first hole-injection layer 131, and the firsthole-transport layer 132.

In this way, the optical path length between the first reflectiveelectrode 104B and the first light-emitting layer 108 may be adjusted bychanging the thicknesses of a plurality of layers between the firstreflective electrode 104B and the first light-emitting layer 108. Thesame applies to the optical path length between the second reflectiveelectrode 104G and the first light-emitting layer 108 and the opticalpath length between the third reflective electrode 104R and the firstlight-emitting layer 108.

As described above, in the light-emitting device 100A, the followingcomponents are provided in each light-emitting element in addition tothe components of the light-emitting device 100: the firsthole-injection layer 131, the first hole-transport layer 132, the firstelectron-transport layer 133, the first electron-injection layer 134,the second hole-injection layer 135, the second hole-transport layer136, the second electron-transport layer 137, and the secondelectron-injection layer 138. The other components are similar to thoseof the light-emitting device 100 illustrated in FIG. 1A, and the effectsimilar to that in the case of the light-emitting device 100 isobtained.

Structural Example 3 of Light-Emitting Device

Next, a structural example different from that of the light-emittingdevice 100A illustrated in FIG. 1B will be described below withreference to FIG. 3.

A light-emitting device 100B illustrated in FIG. 3 includes a partitionwall 120 in addition to the first light-emitting element 101B, thesecond light-emitting element 101G, and the third light-emitting element101R included in the light-emitting device 100A illustrated in FIG. 1B.The light-emitting device 100B also includes a substrate 152 that facesthe substrate 102. The substrate 152 is provided with a light-blockinglayer 154, a first optical element 156B, a second optical element 156G,and a third optical element 156R.

The partition wall 120 has an insulating property. The partition wall120 covers end portions of a lower electrode (the first reflectiveelectrode 104B, the second reflective electrode 104G, the thirdreflective electrode 104R, the first transparent conductive film 106B,the second transparent conductive film 106G, or the third transparentconductive film 106R) of each light-emitting element and has an openingthat overlaps with the lower electrode.

With the partition wall 120, the lower electrodes of the light-emittingelements can be separated into island-shapes.

The light-blocking layer 154 has a function of blocking light from theadjacent light-emitting element. Note that a structure without thelight-blocking layer 154 may also be employed.

The first optical element 156B, the second optical element 156G, and thethird optical element 156R each have a function of selectivelytransmitting light of a particular color out of incident light. With thefirst optical element 156B, the second optical element 156G, and thethird optical element 156R, the color purity of each light-emittingelement can be enhanced.

As described above, in the light-emitting device 100B, the followingcomponents are provided in addition to the components of thelight-emitting device 100A: the partition wall 120 that covers the endportions of the lower electrode of each light-emitting element, and thefirst optical element 156B, the second optical element 156G, and thethird optical element 156R that face the light-emitting elements. Withthe first optical element 156B, the second optical element 156G, and thethird optical element 156R, the color purity of the light-emittingdevice 100B can be enhanced. The other components are similar to thoseof the light-emitting device 100A illustrated in FIG. 1B, and the effectsimilar to that in the case of the light-emitting device 100A isobtained.

Now, other components of the light-emitting device 100 illustrated inFIG. 1A, the light-emitting device 100A illustrated in FIG. 1B, and thelight-emitting device 100B illustrated in FIG. 3 will be described indetail below.

<Substrate>

The substrate 102 is used as a support of the light-emitting elements.The substrate 152 is used as a support of the optical elements. For thesubstrates 102 and 152, for example, glass, quartz, plastics, or thelike can be used. Alternatively, a flexible substrate can be used. Aflexible substrate is a substrate that can be bent, such as a plasticsubstrate made of, for example, polycarbonate, polyarylate, orpoly(ether sulfone). A film made of polypropylene, polyester, polyvinylfluoride, polyvinyl chloride, or the like, an inorganic film formed byevaporation, or the like can also be used. Note that other materials canalso be used as long as they can function as a support in amanufacturing process of the light-emitting elements and the opticalelements.

<Reflective Electrode>

The first reflective electrode 104B, the second reflective electrode104G, and the third reflective electrode 104R each have a function as alower electrode or an anode of each light-emitting element. The firstreflective electrode 104B, the second reflective electrode 104G, and thethird reflective electrode 104R are each formed using a reflectiveconductive material containing silver. Examples of such a conductivematerial include silver (Ag) and an alloy containing silver (Ag) and M(M represents Y, Nd, Mg, Al, Ti, Ga, Zn, In, Mn, W, Sn, Fe, Ni, Cu, Pd,Ir, or Au). Examples of the alloy containing silver include an alloycontaining silver, palladium, and copper, an alloy containing silver andcopper, an alloy containing silver and magnesium, an alloy containingsilver and nickel, and an alloy containing silver and gold.

The first reflective electrode 104B, the second reflective electrode104G, and the third reflective electrode 104R can each be formed using aconductive material whose visible light reflectivity is higher than orequal to 40% and lower than or equal to 100%, preferably higher than orequal to 70% and lower than or equal to 100%, and whose resistivity islower than or equal to 1×10⁻² Ω·cm. The first reflective electrode 104B,the second reflective electrode 104G, and the third reflective electrode104R can each be formed by a sputtering method, an evaporation method, aprinting method, a coating method, or the like.

<Transparent Conductive Film>

The first transparent conductive film 106B, the second transparentconductive film 106G, and the third transparent conductive film 106Reach have a function as a lower electrode or an anode of eachlight-emitting element. In addition, the first transparent conductivefilm 106B, the second transparent conductive film 106G, and the thirdtransparent conductive film 106R each have a function of adjusting theoptical path length so that desired light emitted from eachlight-emitting layer resonates and its wavelength can be amplified.

The first transparent conductive film 106B, the second transparentconductive film 106G, and the third transparent conductive film 106R caneach be formed using, for example, ITO, indium oxide-tin oxidecontaining silicon or silicon oxide (indium tin oxide doped with SiO₂,hereinafter referred to as ITSO), indium oxide-zinc oxide (indium zincoxide), or indium oxide containing tungsten oxide and zinc oxide. Inparticular, the first transparent conductive film 106B, the secondtransparent conductive film 106G, and the third transparent conductivefilm 106R are each preferably formed using a material with a high workfunction (higher than or equal to 4.0 eV). The first transparentconductive film 106B, the second transparent conductive film 106G, andthe third transparent conductive film 106R can each be formed by asputtering method, an evaporation method, a printing method, a coatingmethod, or the like.

<Semi-Transmissive and Semi-Reflective Electrode>

The semi-transmissive and semi-reflective electrode 114 has a functionas an upper electrode or a cathode of each light-emitting element. Thesemi-transmissive and semi-reflective electrode 114 is formed using areflective and light-transmitting conductive material. Alternatively,the semi-transmissive and semi-reflective electrode 114 is formed usinga reflective conductive material and a light-transmitting conductivematerial. Examples of such a conductive material include conductivematerials whose visible light reflectivity is higher than or equal to20% and lower than or equal to 80%, preferably higher than or equal to40% and lower than or equal to 70%, and whose resistivity is lower thanor equal to 1×10⁻² Ω·cm. The semi-transmissive and semi-reflectiveelectrode 114 can be formed using one or more kinds of conductivemetals, conductive alloys, conductive compounds, and the like. Inparticular, it is preferable to use a material with a low work function(lower than or equal to 3.8 eV). Examples of the material includealuminum, silver, an element belonging to Group 1 or 2 of the periodictable (e.g., an alkali metal such as lithium or cesium, an alkalineearth metal such as calcium or strontium, or magnesium), an alloycontaining any of these elements (e.g., Ag—Mg or Al—Li), a rare earthmetal such as europium or ytterbium, and an alloy containing any ofthese rare earth metals. The semi-transmissive and semi-reflectiveelectrode 114 can be formed by a sputtering method, an evaporationmethod, a printing method, a coating method, or the like.

<Light-Emitting Layer>

The first light-emitting layer 108 contains the first light-emittingsubstance that emits light of at least one of violet, blue, and bluegreen, and the second light-emitting layer 112 contains the secondlight-emitting substance that emits light of at least one of green,yellow green, yellow, orange, and red. The first light-emitting layer108 contains one or both of an electron-transport material and ahole-transport material in addition to the first light-emittingsubstance. The second light-emitting layer 112 contains one or both ofan electron-transport material and a hole-transport material in additionto the second light-emitting substance.

As the first light-emitting substance and the second light-emittingsubstance, any of light-emitting substances that convert singletexcitation energy into luminescence and light-emitting substances thatconvert triplet excitation energy into luminescence can be used.Examples of the light-emitting substance are given below.

Examples of the light-emitting substance that converts singletexcitation energy into luminescence include substances that emitfluorescence. For example, the following substances can be used:substances that emit blue light (emission wavelength: greater than orequal to 420 nm and less than or equal to 480 nm) such asN,N-bis[4-(9H-carbazol-9-yl)phenyl]-N,N-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA),410-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylam ine(abbreviation: PCBAPA),4-[4-(10-phenyl-9-anthryl)phenyl]-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPBA), perylene, 2,5,8,11-tetra(tert-butyl)perylene(abbreviation: TBP),N,N-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N-diphenylpyrene-1,6-diamine(abbreviation: 1,6FLPAPrn), andN,N-bis(3-methylphenyl)-N,N-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn); and substances that emit yellow light(emission wavelength: greater than or equal to 550 nm and less than orequal to 580 nm) such as rubrene,5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT),2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile(abbreviation: DCM1), and2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCM2).

Examples of the light-emitting substance that converts tripletexcitation energy into luminescence include substances that emitphosphorescence. For example, a substance having an emission peak atgreater than or equal to 440 nm and less than or equal to 520 nm, asubstance having an emission peak at greater than or equal to 520 nm andless than or equal to 600 nm, or a substance having an emission peak atgreater than or equal to 600 nm and less than or equal to 700 nm can beused.

Examples of the substance that has an emission peak at greater than orequal to 440 nm and less than or equal to 520 nm include organometalliciridium complexes having 4H-triazole skeletons, such astris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III)(abbreviation: Ir(mpptz-dmp)₃),tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: Ir(Mptz)₃), andtris[4-(3-biphenyl)-5-isopropyl-3-phenyl-3-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: Ir(iPrptz-3b)₃); organometallic iridium complexes having1H-triazole skeletons, such astris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: Ir(Mptzl-mp)₃) andtris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III)(abbreviation: Ir(Prptzl-Me)₃); organometallic iridium complexes havingimidazole skeletons, such asfac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III)(abbreviation: Ir(iPrpmi)₃) andtris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III)(abbreviation: Ir(dmpimpt-Me)₃); and organometallic iridium complexes inwhich a phenylpyridine derivative having an electron-withdrawing groupis a ligand, such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III) picolinate(abbreviation: FIrpic),bis[2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)]iridium(III)picolinate (abbreviation: Ir(CF3ppy)₂(pic)), andbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate (abbreviation: FIr(acac)). Among the substances givenabove, the organometallic iridium complex having a 4H-triazole skeletonhas a high reliability and a high emission efficiency and is thusespecially preferable.

Examples of the substance that has an emission peak at greater than orequal to 520 nm and less than or equal to 600 nm include organometalliciridium complexes having pyrimidine skeletons, such astris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation:Ir(mppm)₃), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III)(abbreviation: Ir(tBuppm)₃),(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: Ir(mppm)₂(acac)),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: Ir(tBuppm)₂(acac)),(acetylacetonato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III)(abbreviation: Ir(nbppm)₂(acac)),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: Ir(mpmppm)₂(acac)), and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: Ir(dppm)₂(acac)); organometallic iridium complexes havingpyrazine skeletons, such as(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: Ir(mppr-Me)₂(acac)) and(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: Ir(mppr-iPr)₂(acac)); organometallic iridium complexeshaving pyridine skeletons, such astris(2-phenylpyridinato-N,C^(2′))iridium(III) (abbreviation: Ir(ppy)₃),bis(2-phenylpyridinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(ppy)₂(acac)), bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: Ir(bzq)₂(acac)),tris(benzo[h]quinolinato)iridium(III) (abbreviation: Ir(bzq)₃),tris(2-phenylquinolinato-N,C^(2′))iridium (III) (abbreviation: Ir(pq)₃),and bis(2-phenylquinolinato-N,C^(2′))iridium(II) acetylacetonate(abbreviation: Ir(pq)₂(acac)); and a rare earth metal complex such astris(acetylacetonato) (monophenanthroline)terbium(III) (abbreviation:Tb(acac)₃(Phen)). Among the substances given above, the organometalliciridium complex having a pyrimidine skeleton has distinctively highreliability and emission efficiency and is thus especially preferable.

Among the substances having an emission peak at greater than or equal to520 nm and less than or equal to 600 nm, a substance having an emissionpeak at greater than or equal to 550 nm and less than or equal to 580 nmis especially preferably used. With the use of the substance having anemission peak at greater than or equal to 550 nm and less than or equalto 580 nm, the current efficiency of the light-emitting element can beincreased.

Examples of the substance having an emission peak at greater than orequal to 550 nm and less than or equal to 580 nm includebis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(III) (abbreviation:Ir(dmppm-dmp)₂(acac)).

Examples of the substance that has an emission peak at greater than orequal to 600 nm and less than or equal to 700 nm include organometalliciridium complexes having pyrimidine skeletons, such as(diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III)(abbreviation: Ir(5mdppm)₂(dibm)),bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: Ir(5mdppm)₂(dpm)), andbis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(dlnpm)₂(dpm));organometallic iridium complexes having pyrazine skeletons, such as(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: Ir(tppr)₂(acac)), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr)₂(dpm)), and(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: Ir(Fdpq)₂(acac)); organometallic iridium complexes havingpyridine skeletons, such astris(1-phenylisoquinolinato-N,C²′)iridium(III) (abbreviation: Ir(piq)₃)and bis(1-phenylisoquinolinato-N,C²′)iridium(II)acetylacetonate(abbreviation: Ir(piq)₂(acac)); a platinum complex such as2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II)(abbreviation: PtOEP); and rare earth metal complexes such astris(1,3-diphenyl-1,3-propanedionato) (monophenanthroline)europium(III)(abbreviation: Eu(DBM)₃(Phen)) andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: Eu(TTA)₃(Phen)). Amongthe substances given above, the organometallic iridium complex having apyrimidine skeleton has distinctively high reliability and emissionefficiency and is thus especially preferable. Furthermore, theorganometallic iridium complex having a pyrazine skeleton can providered light emission with favorable chromaticity.

As the electron-transport material used for the first light-emittinglayer 108 and the second light-emitting layer 112, a π-electrondeficient heteroaromatic compound such as a nitrogen-containingheteroaromatic compound is preferable, examples of which includequinoxaline derivatives and dibenzoquinoxaline derivatives such as2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline(abbreviation: 2CzPDBq-III),7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:7mDBTPDBq-II), and6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:6mDBTPDBq-II).

As the hole-transport material used for the first light-emitting layer108 and the second light-emitting layer 112, a π-electron richheteroaromatic compound (e.g., a carbazole derivative or an indolederivative) or an aromatic amine compound is preferable, examples ofwhich include 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBA1BP),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1),4,4′,4″-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation:1′-TNATA),2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9′-bifluorene(abbreviation: DPA2SF),N,N′-bis(9-phenylcarbazol-3-yl)-N,N-diphenylbenzene-1,3-diamine(abbreviation: PCA2B),N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine(abbreviation: DPNF),N,N′-triphenyl-N,N′,N″-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine(abbreviation: PCA3B),2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: PCASF),2-[N-(4diphenylaminophenyl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: DPASF),N,N′-bis[4-(carbazol-9-yl)phenyl]-N,N′-diphenyl-9,9-dimethylfluorene-2,7-diamine(abbreviation: YGA2F),4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbreviation: TPD),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB),N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N-phenyl-N′-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine(abbreviation: DFLADFL),3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA1),3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA2),4,4′-bis(N-{4-[AP-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl(abbreviation: DNTPD),3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole(abbreviation: PCzTPN2), and3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2).

<Hole-Injection Layer and Hole-Transport Layer>

The first hole-injection layer 131 injects holes into the firstlight-emitting layer 108 through the first hole-transport layer 132 witha high hole-transport property and contains a hole-transport materialand an acceptor material. The first hole-injection layer 131 contains ahole-transport material and an acceptor material, so that electrons areextracted from the hole-transport material by the acceptor material togenerate holes, and the holes are injected into the first light-emittinglayer 108 through the first hole-transport layer 132. The firsthole-injection layer 131 may have a structure in which a hole-transportmaterial and an acceptor material are stacked. The first hole-transportlayer 132 is formed using a hole-transport material. The secondhole-injection layer 135 injects holes into the second light-emittinglayer 112 through the second hole-transport layer 136 with a highhole-transport property and contains a hole-transport material and anacceptor material. The second hole-injection layer 135 contains ahole-transport material and an acceptor material, so that electrons areextracted from the hole-transport material by the acceptor material togenerate holes, and the holes are injected into the secondlight-emitting layer 112 through the second hole-transport layer 136.The second hole-injection layer 135 may have a structure in which ahole-transport material and an acceptor material are stacked. The secondhole-transport layer 136 is formed using a hole-transport material.

Examples of the hole-transport material used for the firsthole-injection layer 131, the first hole-transport layer 132, the secondhole-injection layer 135, and the second hole-transport layer 136include aromatic amine compounds such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD),N,N-bis(3-methylphenyl)-N,N-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA), and4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB);3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1);3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2); and3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1). Examples further include carbazole derivativessuch as 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), and9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-Carbazole (abbreviation: CzPA).The substances described here are mainly substances having a holemobility of higher than or equal to 1×10⁶ cm²/Vs. Note that othersubstances may also be used as long as their hole-transport propertiesare higher than their electron-transport properties.

Furthermore, a high molecular compound such as poly(N-vinylcarbazole)(abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD) can be used.

Examples of the acceptor material used for the first hole-injectionlayer 131 and the second hole-injection layer 135 include compoundshaving an electron-withdrawing group (a halogen group or a cyano group)such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane(abbreviation: F₄-TCNQ), chloranil, and2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN). Inparticular, a compound in which electron-withdrawing groups are bondedto a condensed aromatic ring having a plurality of hetero atoms, likeHAT-CN, is thermally stable and preferable. A transition metal oxide canalso be used. Oxides of metals belonging to Groups 4 to 8 of theperiodic table can also be used. Specifically, it is preferable to usevanadium oxide, niobium oxide, tantalum oxide, chromium oxide,molybdenum oxide, tungsten oxide, manganese oxide, or rhenium oxidebecause of their high electron-accepting properties. Molybdenum oxide isespecially preferable because it is stable in the air, has a lowhygroscopic property, and is easy to handle.

The first hole-injection layer 131 and the second hole-injection layer135 may also be formed using the above-described acceptor material aloneor using the above-described acceptor material and another material incombination. In that case, the acceptor material extracts electrons fromthe hole-transport layer, so that holes can be injected into thehole-transport layer. The acceptor material transfers the extractedelectrons to the anode.

<Electron-Transport Layer>

The first electron-transport layer 133 and the second electron-transportlayer 137 each contain a substance with a high electron-transportproperty. The first electron-transport layer 133 and the secondelectron-transport layer 137 can each be formed using a metal complexsuch as Alq₃, tris(4-methyl-8-quinolinolato)aluminum (abbreviation:Almq₃), bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation:BeBq2), BAlq, bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation:Zn(BOX)₂), or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation:Zn(BTZ)₂). Furthermore, a heteroaromatic compound such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: Bphen),bathocuproine (abbreviation: BCP), or4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) can beused. Furthermore, a high molecular compound such aspoly(2,5-pyridinediyl) (abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py), orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can be used. The substances mentioned here aremainly substances having an electron mobility of higher than or equal to1×10⁻⁶ cm²/Vs. Note that other substances may also be used for the firstelectron-transport layer 133 and the second electron-transport layer 137as long as their electron-transport properties are higher than theirhole-transport properties.

The first electron-transport layer 133 and the second electron-transportlayer 137 are not limited to a single layer, and may be a stack of twoor more layers containing any of the above substances.

<Electron-Injection Layer>

The first electron-injection layer 134 and the second electron-injectionlayer 138 each contain a substance with a high electron-injectionproperty. The first electron-injection layer 134 and the secondelectron-injection layer 138 can each be formed using an alkali metal,an alkaline earth metal, or a compound thereof, such as lithium fluoride(LiF), cesium fluoride (CsF), calcium fluoride (CaF₂), or lithium oxide(LiOn). Furthermore, a rare earth metal compound such as erbium fluoride(ErF₃) can be used. An electride may also be used for the firstelectron-injection layer 134 and the second electron-injection layer138. Examples of the electride include a substance in which electronsare added at a high concentration to calcium oxide-aluminum oxide.

A composite material in which an organic compound and an electron donor(donor) are mixed may also be used for the first electron-injectionlayer 134 and the second electron-injection layer 138. Such a compositematerial is excellent in electron-injection property andelectron-transport property, since electrons are generated in theorganic compound by the electron donor. The organic compound in such acase is preferably a material excellent in transporting the generatedelectrons, specific examples of which include a substance for formingthe first electron-transport layer 133 and the second electron-transportlayer 137 (e.g., a metal complex or a heteroaromatic compound), which isdescribed above. As the electron donor, a substance showing anelectron-donating property with respect to the organic compound may beused. Specifically, an alkali metal, an alkaline earth metal, and a rareearth metal are preferable, and lithium, cesium, magnesium, calcium,erbium, ytterbium, and the like can be given. Furthermore, an alkalimetal oxide and an alkaline earth metal oxide are preferable, andlithium oxide, calcium oxide, barium oxide, and the like can be given.Lewis base such as magnesium oxide can also be used. An organic compoundsuch as tetrathiafulvalene (abbreviation: TTF) can also be used.

<Charge-Generation Layer>

The charge-generation layer 110 has a function of injecting electronsinto one of the light-emitting layers (the first light-emitting layer108 or the second light-emitting layer 112) and injecting holes into theother light-emitting layer (the first light-emitting layer 108 or thesecond light-emitting layer 112), when a voltage is applied between thepair of electrodes (the lower electrode and the upper electrode).

For example, in the first light-emitting element 101B illustrated inFIG. 1A, when a voltage is applied such that the potential of the lowerelectrode (the first reflective electrode 104B and the first transparentconductive film 106B) is higher than that of the semi-transmissive andsemi-reflective electrode 114, the charge-generation layer 110 injectselectrons into the first light-emitting layer 108 and injects holes intothe second light-emitting layer 112. In the first light-emitting element101B illustrated in FIG. 1B, when a voltage is applied such that thepotential of the lower electrode (the first reflective electrode 104Band the first transparent conductive film 106B) is higher than that ofthe semi-transmissive and semi-reflective electrode 114, thecharge-generation layer 110 injects electrons into the firstelectron-injection layer 134 and injects holes into the secondhole-injection layer 135.

Note that in terms of light extraction efficiency, the charge-generationlayer 110 preferably transmits visible light (specifically, thecharge-generation layer 110 has a visible light transmittance of higherthan or equal to 40%). The charge-generation layer 110 functions even ifit has lower conductivity than the pair of electrodes (the lowerelectrode and the upper electrode).

The charge-generation layer 110 may have either a structure in which anelectron acceptor (acceptor) is added to a hole-transport material or astructure in which an electron donor (donor) is added to anelectron-transport material. Alternatively, both of these structures maybe stacked.

By forming the charge-generation layer 110 using any of the abovematerials, it is possible to suppress an increase in driving voltagecaused when the light-emitting layers are stacked.

The above-described light-emitting layer, hole-transport layer,hole-injection layer, electron-transport layer, electron-injectionlayer, and charge-generation layer can each be formed by any of thefollowing methods: a sputtering method, an evaporation method (includinga vacuum evaporation method), a printing method (such as reliefprinting, intaglio printing, gravure printing, planography printing, andstencil printing), an ink-jet method, a coating method, and the like.

<Light-Blocking Layer>

The light-blocking layer 154 has a function of blocking light emittedfrom the adjacent light-emitting element and preventing mixture oflight. In addition, the light-blocking layer 154 has a function ofreducing the reflection of external light. As the light-blocking layer154, a metal, a resin containing black pigment, carbon black, a metaloxide, a composite oxide containing a solid solution of a plurality ofmetal oxides, or the like can be used.

<Optical Element>

The first optical element 156B, the second optical element 156G, and thethird optical element 156R each selectively transmit light of aparticular color out of incident light. For example, a color filter, aband pass filter, a multilayer filter, or the like can be used. Colorconversion elements can also be used as the optical elements. A colorconversion element is an optical element that converts incident lightinto light having a longer wavelength than the incident light. As thecolor conversion elements, quantum-dot elements are favorably used. Theusage of the quantum-dot elements can increase the color reproducibilityof the light-emitting device.

The first optical element 156B transmits blue light out of light emittedfrom the first light-emitting element 101B. The second optical element156G transmits green light out of light emitted from the secondlight-emitting element 101G. The third optical element 156R transmitsred light out of light emitted from the third light-emitting element101R.

A plurality of optical elements may also be stacked over each of thefirst light-emitting element 101B, the second light-emitting element101G, and the third light-emitting element 101R. As the optical element,a circularly polarizing plate, an anti-reflective film, or the like canalso be used, for example. A circularly polarizing plate provided on theside where light emitted from the light-emitting element of thelight-emitting device is extracted can prevent a phenomenon in whichlight entering from the outside of the light-emitting device isreflected in the light-emitting device and emitted to the outside. Ananti-reflective film can weaken external light reflected by a surface ofthe light-emitting device. Accordingly, light emitted from thelight-emitting device can be observed clearly.

Structural Example 4 of Light-Emitting Device

Next, a structural example different from that of the light-emittingdevice 100 illustrated in FIG. 1A will be described below with referenceto FIG. 4A.

FIG. 4A is a cross-sectional view illustrating an example of alight-emitting device according to one embodiment of the presentinvention. A light-emitting device 160 illustrated in FIG. 4A includesthe first light-emitting element 101B having a function of emitting bluelight, the second light-emitting element 101G having a function ofemitting green light, the third light-emitting element 101R having afunction of emitting red light, and a fourth light-emitting element 101Yhaving a function of emitting yellow light.

The first light-emitting element 101B, the second light-emitting element101G, and the third light-emitting element 101R have structures similarto those of the first light-emitting element 101B, the secondlight-emitting element 101G, and the third light-emitting element 101R,respectively, illustrated in FIG. 1A. The fourth light-emitting element101Y includes a fourth reflective electrode 104Y, a fourth transparentconductive film 106Y over the fourth reflective electrode 104Y, thefirst light-emitting layer 108 over the fourth transparent conductivefilm 106Y, the charge-generation layer 110 over the first light-emittinglayer 108, the second light-emitting layer 112 over thecharge-generation layer 110, and the semi-transmissive andsemi-reflective electrode 114 over the second light-emitting layer 112.

The first reflective electrode 104B, the second reflective electrode104G, the third reflective electrode 104R, and the fourth reflectiveelectrode 104Y each contain silver. When the first reflective electrode104B, the second reflective electrode 104G, the third reflectiveelectrode 104R, and the fourth reflective electrode 104Y are each formedusing a material containing silver, the reflectivity can be increasedand the emission efficiency of each light-emitting element can beincreased. For example, a conductive film containing silver is formedand separated into an island-shape; in this way, the first reflectiveelectrode 104B, the second reflective electrode 104G, the thirdreflective electrode 104R, and the fourth reflective electrode 104Y canbe formed. The first reflective electrode 104B, the second reflectiveelectrode 104G, the third reflective electrode 104R, and the fourthreflective electrode 104Y are preferably formed through a step ofprocessing the same conductive film, because the manufacturing cost canbe reduced.

In FIG. 4A, the second light-emitting layer 112 includes the secondlight-emitting layer 112 a and the second light-emitting layer 112 b.The second light-emitting layer 112 can have a single-layer structure, astacked structure including two layers as illustrated in FIG. 4A, or astacked structure including three or more layers.

In FIG. 4A, the first light-emitting layer 108, the charge-generationlayer 110, the second light-emitting layer 112, and thesemi-transmissive and semi-reflective electrode 114 are separated forthe first to fourth light-emitting elements 101B to 101Y; however, theycan also be used without being separated. Therefore, in the secondlight-emitting element 101G, the third light-emitting element 101R, andthe fourth light-emitting element 101Y, the first light-emitting layer108, the charge-generation layer 110, the second light-emitting layer112, and the semi-transmissive and semi-reflective electrode 114 arerepresented by the same hatching patterns as in the first light-emittingelement 101B and not especially denoted by reference numerals.

As described above, in the light-emitting device 160 illustrated in FIG.4A, the fourth light-emitting element 101Y is provided in addition tothe components of the light-emitting device 100 illustrated in FIG. 1A.

The fourth light-emitting element 101Y in the light-emitting device 160will be described in detail below.

The fourth light-emitting element 101Y has a microcavity structure.Light emitted from the first light-emitting layer 108 and the secondlight-emitting layer 112 resonates between a pair of electrodes (betweenthe fourth reflective electrode 104Y and the semi-transmissive andsemi-reflective electrode 114). In the light-emitting device 160, thethickness of the fourth transparent conductive film 106Y in the fourthlight-emitting element 101Y is adjusted so that a desired emissionwavelength of light emitted from the first light-emitting layer 108 andthe second light-emitting layer 112 can be amplified.

Specifically, the thickness of the fourth transparent conductive film106Y is adjusted so that the optical path length between the fourthreflective electrode 104Y and the semi-transmissive and semi-reflectiveelectrode 114 can be m_(w)λ_(Y)/2 (m_(w) is a natural number and λ_(Y)is a wavelength (greater than or equal to 550 nm and less than or equalto 580 nm) of yellow light).

By adjusting the thickness of the fourth transparent conductive film106Y, the optical path length between the fourth reflective electrode104Y and the first light-emitting layer 108 can be less than ¾λ_(Y),preferably greater than or equal to ¼λ_(Y) and less than ¾λ_(Y). Byadjusting the thickness of the fourth transparent conductive film 106Y,the optical path length between the fourth reflective electrode 104Y andthe second light-emitting layer 112 can be around ¾λ_(Y). When theoptical path length is set as described above, yellow light can beefficiently extracted from the second light-emitting substance containedin the second light-emitting layer 112 in the fourth light-emittingelement 101Y.

As described above, the fourth transparent conductive film 106Y has afunction of adjusting the optical path length in the fourthlight-emitting element 101Y. When the optical path length is adjusted ineach light-emitting element, the first transparent conductive film 106Bis formed to be thicker than the third transparent conductive film 106R,the third transparent conductive film 106R is formed to be thicker thanthe fourth transparent conductive film 106Y, and the fourth transparentconductive film 106Y is formed to be thicker than the second transparentconductive film 106G. In other words, the first transparent conductivefilm 106B has a first region, the second transparent conductive film106G has a second region, the third transparent conductive film 106R hasa third region, and the fourth transparent conductive film 106Y has afourth region; the first region is thicker than the third region, thethird region is thicker than the fourth region, and the fourth region isthicker than the second region.

As described above, in the light-emitting device 160, the fourthlight-emitting element 101Y is provided in addition to the components ofthe light-emitting device 100. The other components are similar to thoseof the light-emitting device 100 illustrated in FIG. 1A, and the effectsimilar to that in the case of the light-emitting device 100 isobtained.

Structural Example 5 of Light-Emitting Device

Next, a structural example different from that of the light-emittingdevice 160 illustrated in FIG. 4A will be described below with referenceto FIG. 4B.

FIG. 4B is a cross-sectional view illustrating an example of alight-emitting device according to one embodiment of the presentinvention. In FIG. 4B, a portion having a function similar to that inFIG. 4A is represented by the same hatch pattern as in FIG. 4A and notespecially denoted by a reference numeral in some cases. In addition,common reference numerals are used for portions having similarfunctions, and a detailed description of the portions is omitted in somecases.

A light-emitting device 160A illustrated in FIG. 4B includes the firstlight-emitting element 101B having a function of emitting blue light,the second light-emitting element 101G having a function of emittinggreen light, the third light-emitting element 101R having a function ofemitting red light, and the fourth light-emitting element 101Y having afunction of emitting yellow light.

The first light-emitting element 101B, the second light-emitting element101G, and the third light-emitting element 101R have structures similarto those of the first light-emitting element 101B, the secondlight-emitting element 101G, and the third light-emitting element 101R,respectively, illustrated in FIG. 1B. The fourth light-emitting element101Y includes the fourth reflective electrode 104Y, the fourthtransparent conductive film 106Y over the fourth reflective electrode104Y, the first hole-injection layer 131 over the fourth transparentconductive film 106Y, the first hole-transport layer 132 over the firsthole-injection layer 131, the first light-emitting layer 108 over thefirst hole-transport layer 132, the first electron-transport layer 133over the first light-emitting layer 108, the first electron-injectionlayer 134 over the first electron-transport layer 133, thecharge-generation layer 110 over the first electron-injection layer 134,the second hole-injection layer 135 over the charge-generation layer110, the second hole-transport layer 136 over the second hole-injectionlayer 135, the second light-emitting layer 112 over the secondhole-transport layer 136, the second electron-transport layer 137 overthe second light-emitting layer 112, the second electron-injection layer138 over the second electron-transport layer 137, and thesemi-transmissive and semi-reflective electrode 114 over the secondelectron-injection layer 138.

In the light-emitting device 160A, the optical path length between thefourth reflective electrode 104Y and the first light-emitting layer 108is adjusted with the thickness of at least one of the fourth transparentconductive film 106Y, the first hole-injection layer 131, and the firsthole-transport layer 132.

In this way, the optical path length between the fourth reflectiveelectrode 104Y and the first light-emitting layer 108 may be adjusted bychanging the thicknesses of a plurality of layers between the fourthreflective electrode 104Y and the first light-emitting layer 108.

As described above, in the light-emitting device 160A, the followingcomponents are provided in each light-emitting element in addition tothe components of the light-emitting device 160: the firsthole-injection layer 131, the first hole-transport layer 132, the firstelectron-transport layer 133, the first electron-injection layer 134,the second hole-injection layer 135, the second hole-transport layer136, the second electron-transport layer 137, and the secondelectron-injection layer 138. The other components are similar to thoseof the light-emitting device 160 illustrated in FIG. 4A, and the effectsimilar to that in the case of the light-emitting device 160 isobtained.

Structural Example 6 of Light-Emitting Device

Next, a structural example different from that of the light-emittingdevice 160A illustrated in FIG. 4B will be described below withreference to FIG. 5.

A light-emitting device 160B illustrated in FIG. 5 includes thepartition wall 120 in addition to the first light-emitting element 101B,the second light-emitting element 101G, the third light-emitting element101R, and the fourth light-emitting element 101Y included in thelight-emitting device 160A illustrated in FIG. 4B. The light-emittingdevice 160B also includes the substrate 152 that faces the substrate102. The substrate 152 is provided with the light-blocking layer 154,the first optical element 156B, the second optical element 156G, thethird optical element 156R, and a fourth optical element 156Y.

The partition wall 120, the light-blocking layer 154, the first opticalelement 156B, the second optical element 156G, and the third opticalelement 156R can have structures similar to those of the light-emittingdevice 100B illustrated in FIG. 3. The fourth optical element 156Y has afunction of selectively transmitting light of a particular color out ofincident light. With the fourth optical element 156Y, the color purityof the fourth light-emitting element 101Y can be enhanced.

As described above, in the light-emitting device 160B, the followingcomponents are provided in addition to the components of thelight-emitting device 160: the partition wall 120 that covers the endportions of the lower electrode of each light-emitting element, and thefirst optical element 156B, the second optical element 156G, the thirdoptical element 156R, and the fourth optical element 156Y that face thelight-emitting elements. The other components are similar to those ofthe light-emitting device 160 illustrated in FIG. 4A, and the effectsimilar to that in the case of the light-emitting device 160 isobtained.

Structural Example 7 of Light-Emitting Device

Next, a structural example different from that of the light-emittingdevice 160B illustrated in FIG. 5 will be described below with referenceto FIG. 6.

In a light-emitting device 160C illustrated in FIG. 6, the fourthoptical element 156Y included in the light-emitting device 160Billustrated in FIG. 5 is not provided. The other components are similarto those of the light-emitting device 160B illustrated in FIG. 5, andthe effect similar to that in the case of the light-emitting device 160Bis obtained.

Since the fourth optical element 156Y that overlaps with the fourthlight-emitting element 101Y is not provided, less energy of lightemitted from the fourth light-emitting element 101Y is lost than in thestructure with the fourth optical element 156Y, leading to a lower powerconsumption.

Structural Example 8 of Light-Emitting Device

Next, a structural example different from that of the light-emittingdevice 160C illustrated in FIG. 6 will be described below with referenceto FIG. 7.

A light-emitting device 160D illustrated in FIG. 7 includes a fifthlight-emitting element 101W instead of the fourth light-emitting element101Y included in the light-emitting device 160C illustrated in FIG. 6.

The fifth light-emitting element 101W includes a fifth reflectiveelectrode 104W, a fifth transparent conductive film 106W over the fifthreflective electrode 104W, the first hole-injection layer 131 over thefifth transparent conductive film 106W, the first hole-transport layer132 over the first hole-injection layer 131, the first light-emittinglayer 108 over the first hole-transport layer 132, the firstelectron-transport layer 133 over the first light-emitting layer 108,the first electron-injection layer 134 over the first electron-transportlayer 133, the charge-generation layer 110 over the firstelectron-injection layer 134, the second hole-injection layer 135 overthe charge-generation layer 110, the second hole-transport layer 136over the second hole-injection layer 135, the second light-emittinglayer 112 over the second hole-transport layer 136, the secondelectron-transport layer 137 over the second light-emitting layer 112,the second electron-injection layer 138 over the secondelectron-transport layer 137, and the semi-transmissive andsemi-reflective electrode 114 over the second electron-injection layer138.

In the fifth light-emitting element 101W, the optical path lengthbetween the fifth reflective electrode 104W and the first light-emittinglayer 108 is adjusted with the thickness of at least one of the fifthtransparent conductive film 106W, the first hole-injection layer 131,and the first hole-transport layer 132.

For example, the thickness of the fifth transparent conductive film 106Wis substantially the same as that of the third transparent conductivefilm 106R. In the fifth light-emitting element 101W, light emission fromthe first light-emitting substance contained in the first light-emittinglayer 108 and light emission from the second light-emitting substancecontained in the second light-emitting layer 112 are combined so thatwhite light emission can be obtained.

In addition, no optical element is provided to overlap with the fifthlight-emitting element 101W. Therefore, less energy of light emittedfrom the fifth light-emitting element 101W is lost than in the firstlight-emitting element 101B, the second light-emitting element 101G, andthe third light-emitting element 101R, leading to a lower powerconsumption.

The above-described structures of the light-emitting devices can becombined as appropriate.

<Manufacturing Method 1 of Light-Emitting Device>

Next, a method for manufacturing a light-emitting device according toone embodiment of the present invention will be described below withreference to FIGS. 8A to 8D and FIGS. 9A and 9B. Here, a method formanufacturing the light-emitting device 160B illustrated in FIG. 5 willbe described.

FIGS. 8A to 8D and FIGS. 9A and 9B are cross-sectional viewsillustrating a method for manufacturing the light-emitting deviceaccording to one embodiment of the present invention.

The method for manufacturing the light-emitting device 160B describedbelow includes first to seventh steps.

<First Step>

In the first step, a reflective electrode (e.g., the first reflectiveelectrode 104B, the second reflective electrode 104G, the thirdreflective electrode 104R, or the fourth reflective electrode 104Y) ofeach light-emitting element is formed over the substrate 102 (see FIG.8A).

In this embodiment, a reflective conductive film is formed over thesubstrate 102 and processed into a desired shape; in this way, the firstreflective electrode 104B, the second reflective electrode 104G, thethird reflective electrode 104R, and the fourth reflective electrode104Y are formed. As the reflective conductive film, an alloy film ofsilver, palladium, and copper is used.

Note that a plurality of transistors may be formed over the substrate102 before the first step. The plurality of transistors may beelectrically connected to the first reflective electrode 104B, thesecond reflective electrode 104G, the third reflective electrode 104R,and the fourth reflective electrode 104Y.

<Second Step>

In the second step, a transparent conductive film (e.g., the firsttransparent conductive film 106B, the second transparent conductive film106G, the third transparent conductive film 106R, or the fourthtransparent conductive film 106Y) of each light-emitting element isformed over the reflective electrode (see FIG. 8B).

In this embodiment, a transparent conductive film is formed over thesubstrate 102, the first reflective electrode 104B, the secondreflective electrode 104G, the third reflective electrode 104R, and thefourth reflective electrode 104Y and processed into a desired shape; inthis way, the first transparent conductive film 106B, the secondtransparent conductive film 106G, the third transparent conductive film106R, and the fourth transparent conductive film 106Y are formed. As thetransparent conductive film, an ITSO film is used in this embodiment.

The first transparent conductive film 106B, the second transparentconductive film 106G, the third transparent conductive film 106R, andthe fourth transparent conductive film 106Y may be formed through aplurality of steps. When the first transparent conductive film 106B, thesecond transparent conductive film 106G, the third transparentconductive film 106R, and the fourth transparent conductive film 106Yare formed through a plurality of steps, they can be formed to havethicknesses which enable each light-emitting element to have amicrocavity structure.

<Third Step>

In the third step, the partition wall 120 that covers end portions of alower electrode (e.g., the first reflective electrode 104B, the secondreflective electrode 104G, the third reflective electrode 104R, thefourth reflective electrode 104Y, the first transparent conductive film106B, the second transparent conductive film 1060, the third transparentconductive film 106R, or the fourth transparent conductive film 106Y) ofeach light-emitting element is formed (see FIG. 8C).

The partition wall 120 includes an opening that overlaps with the lowerelectrode. The transparent conductive film that overlaps with theopening functions as the lower electrode of the light-emitting element.In this embodiment, an acrylic resin is used as the partition wall 120.

In the first to third steps, since there is no possibility of damaging alight-emitting layer containing an organic compound, a variety of filmformation methods and micromachining technologies can be employed. Inthis embodiment, a reflective conductive film is formed by a sputteringmethod, a pattern is formed over the reflective conductive film by alithography method, and then the reflective conductive film is processedinto an island shape by a dry etching method or a wet etching method toform the first reflective electrode 104B, the second reflectiveelectrode 104G, the third reflective electrode 104R, and the fourthreflective electrode 104Y. Then, a transparent conductive film is formedby a sputtering method, a pattern is formed over the transparentconductive film by a lithography method, and then the transparentconductive film is processed into an island shape by a wet etchingmethod to form the first transparent conductive film 106B, the secondtransparent conductive film 106G, the third transparent conductive film106R, and the fourth transparent conductive film 106Y.

<Fourth Step>

In the fourth step, the first hole-injection layer 131, the firsthole-transport layer 132, the first light-emitting layer 108, the firstelectron-transport layer 133, the first electron-injection layer 134,and the charge-generation layer 110 are formed (see FIG. 8D).

The first hole-injection layer 131 can be formed by co-evaporating ahole-transport material and a material containing an acceptor substance.Note that co-evaporation is an evaporation method in which a pluralityof different substances are concurrently vaporized from their respectiveevaporation sources. The first hole-transport layer 132 can be formed byevaporating a hole-transport material.

The first light-emitting layer 108 can be formed by evaporating thefirst light-emitting substance that emits light of at least one ofviolet, blue, and blue green. As the first light-emitting substance, afluorescent organic compound can be used. The fluorescent organiccompound may be evaporated alone or the fluorescent organic compoundmixed with another material may be evaporated. For example, thefluorescent organic compound may be used as a guest material, and theguest material may be dispersed into a host material having a higherexcitation energy than the guest material and evaporated.

The first electron-transport layer 133 can be formed by evaporating asubstance with a high electron-transport property. The firstelectron-injection layer 134 can be formed by evaporating a substancewith a high electron-injection property.

The charge-generation layer 110 can be formed by evaporating a materialobtained by adding an electron acceptor (acceptor) to a hole-transportmaterial or a material obtained by adding an electron donor (donor) toan electron-transport material.

<Fifth Step>

In the fifth step, the second hole-injection layer 135, the secondhole-transport layer 136, the second light-emitting layer 112, thesecond electron-transport layer 137, the second electron-injection layer138, and the semi-transmissive and semi-reflective electrode 114 areformed (see FIG. 9A).

The second hole-injection layer 135 can be formed by using a materialand a method which are similar to those of the first hole-injectionlayer 131. The second hole-transport layer 136 can be formed by using amaterial and a method which are similar to those of the firsthole-transport layer 132.

The second light-emitting layer 112 can be formed by evaporating thesecond light-emitting substance that emits light of at least one ofgreen, yellow green, yellow, orange, and red. As the secondlight-emitting substance, a phosphorescent organic compound can be used.The phosphorescent organic compound may be evaporated alone or thephosphorescent organic compound mixed with another material may beevaporated. For example, the phosphorescent organic compound may be usedas a guest material, and the guest material may be dispersed into a hostmaterial having a higher excitation energy than the guest material andevaporated.

The second electron-transport layer 137 can be formed by evaporating asubstance with a high electron-transport property. The secondelectron-injection layer 138 can be formed by evaporating a substancewith a high electron-injection property.

The semi-transmissive and semi-reflective electrode 114 can be formed bystacking a reflective conductive film and a light-transmittingconductive film. The semi-transmissive and semi-reflective electrode 114may have a single-layer structure or a stacked structure.

Through the above-described steps, the first light-emitting element101B, the second light-emitting element 101G, the third light-emittingelement 101R, and the fourth light-emitting element 101Y are formed overthe substrate 102.

<Sixth Step>

In the sixth step, the light-blocking layer 154, the first opticalelement 156B, the second optical element 156G, the third optical element156R, and the fourth optical element 156Y are formed over the substrate152 (see FIG. 9B).

As the light-blocking layer 154, an organic resin film containing blackpigment is formed in a desired region. Then, the first optical element156B, the second optical element 156G, the third optical element 156R,and the fourth optical element 156Y are formed over the substrate 152and the light-blocking layer 154. As the first optical element 156B, anorganic resin film containing blue pigment is formed in a desiredregion. As the second optical element 156, an organic resin filmcontaining green pigment is formed in a desired region. As the thirdoptical element 156R, an organic resin film containing red pigment isformed in a desired region. As the fourth optical element 156Y, anorganic resin film containing yellow pigment is formed in a desiredregion.

<Seventh Step>

In the seventh step, the first light-emitting element 101B, the secondlight-emitting element 101G, the third light-emitting element 101R, andthe fourth light-emitting element 101Y formed over the substrate 102 areattached to the light-blocking layer 154, the first optical element156B, the second optical element 156G, the third optical element 156R,and the fourth optical element 156Y formed over the substrate 152, andsealed with a sealant (not shown).

Through the above steps, the light-emitting device 160B illustrated inFIG. 5 can be formed.

This embodiment can be combined as appropriate with any of the otherembodiments.

Embodiment 2

In this embodiment, a top view and a cross-sectional view of a displaydevice (also referred to as a display panel or a light-emitting panel)which is one embodiment of a light-emitting device will be describedwith reference to FIGS. 10A and 10B.

FIG. 10A is a top view of a light-emitting panel in which alight-emitting element provided over a first substrate 501 and anoptical element provided over a second substrate 506 are sealed with asealant. FIG. 10B is a cross-sectional view along dashed-dotted lineA1-A2 in FIG. 10A.

The first substrate 501 is provided with a pixel portion 502, a signalline driver circuit portion 503, and scan line driver circuit portions504 a and 504 b. The second substrate 506 is provided with alight-blocking layer 521, a first optical element 522B having a functionof transmitting blue light, a second optical element 522G having afunction of transmitting green light, and a third optical element 522Rhaving a function of transmitting red light. The first substrate 501 andthe second substrate 506 are sealed with a sealant 505.

The pixel portion 502, the signal line driver circuit portion 503, andthe scan line driver circuit portions 504 a and 504 b are sealed withthe first substrate 501, the second substrate 506, the sealant 505, anda filler 507.

An epoxy-based resin or a glass frit is preferably used for the sealant505. It is preferable that such a material do not transmit moisture oroxygen as much as possible.

For the filler 507, an inert gas such as nitrogen or argon, or anultraviolet curable resin or a thermosetting resin can be used. Forexample, a polyvinyl chloride (PVC)-based resin, an acrylic-based resin,a polyimide-based resin, an epoxy-based resin, a silicone-based resin, apolyvinyl butyral (PVB)-based resin, or an ethylene vinyl acetate(EVA)-based resin can be used.

As the signal line driver circuit portion 503 and the scan line drivercircuit portions 504 a and 504 b, driver circuits formed by using asingle crystal semiconductor film or a polycrystalline semiconductorfilm over a separately prepared substrate may be mounted.

The pixel portion 502, the signal line driver circuit portion 503, andthe scan line driver circuit portions 504 a and 504 b each include aplurality of transistors, and FIG. 10B illustrates transistors 510, 511and 512 included in the pixel portion 502 and a transistor 509 includedin the signal line driver circuit portion 503 as an example.

In FIG. 10B, as an example of the transistor, an inverted staggeredtransistor is illustrated but one embodiment of the present invention isnot limited thereto, and a staggered transistor may be used. Inaddition, there is no particular limitation on the polarity of thetransistor. A structure including an n-channel transistor and ap-channel transistor, a structure including only an n-channeltransistor, or a structure including only a p-channel transistor may beused. Furthermore, there is no particular limitation on thecrystallinity of a semiconductor film used for the transistor. Forexample, an amorphous semiconductor film or a crystalline semiconductorfilm can be used. Examples of a semiconductor material include Group 13semiconductors (e.g., gallium), Group 14 semiconductors (e.g., silicon),compound semiconductors (including oxide semiconductors), and organicsemiconductors. For example, an oxide semiconductor that has an energygap of greater than or equal to 2 eV, preferably greater than or equalto 2.5 eV, more preferably greater than or equal to 3 eV is preferablyused for the transistors 509, 510, 511, and 512, because the off-statecurrent of the transistors can be reduced. Examples of the oxidesemiconductor include an In—Ga oxide and an In-M-Zn oxide (M representsAl, Ga, Y, Zr, La, Ce, or Nd).

A variety of signals and potentials are supplied from an FPC 518 to thesignal line driver circuit portion 503, the scan line driver circuitportions 504 a and 504 b, and the pixel portion 502.

The FPC 518 is electrically connected to a terminal electrode 525through an anisotropic conductive film 519 and a connection terminalelectrode 517. The connection terminal electrode 517 is formed through astep of processing the same conductive film as source electrodes anddrain electrodes of the transistors 510, 511 and 512. The terminalelectrode 525 is formed through a step of processing the same conductivefilm as gate electrodes of the transistors 510, 511 and 512.

As the first substrate 501 and the second substrate 506, a semiconductorsubstrate (e.g., a single crystal substrate or a silicon substrate), anSOI substrate, a glass substrate, a quartz substrate, a plasticsubstrate, a metal substrate, a stainless steel substrate, a substrateincluding stainless steel foil, a tungsten substrate, a substrateincluding tungsten foil, a flexible substrate, an attachment film, paperincluding a fibrous material, a base material film, or the like can beused. Examples of a glass substrate include a barium borosilicate glasssubstrate, an aluminoborosilicate glass substrate, and a soda lime glasssubstrate. Examples of the flexible substrate, the attachment film, andthe base material film are as follows: plastics typified by polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), and polyethersulfone (PES), a synthetic resin such as acrylic, polypropylene,polyester, polyvinyl fluoride, polyvinyl chloride, polyamide, polyimide,aramid, epoxy, an inorganic film formed by evaporation, and paper.

When the above-described flexible substrate is used as a substrate overwhich a light-emitting element or a transistor is formed, thelight-emitting element or the transistor may be directly formed over theflexible substrate. Alternatively, part of or the entire light-emittingelement or transistor may be formed over a base substrate with aseparation layer provided therebetween and then the light-emittingelement or the transistor may be separated from the base substrate andtransferred to another substrate. When the light-emitting element or thetransistor is transferred to another substrate by using a separationlayer as described above, the light-emitting element or the transistorcan be formed over a substrate having low heat resistance or a flexiblesubstrate over which the light-emitting element or the transistor isdirectly formed with difficulty. Examples of the above separation layerinclude a stack including inorganic films, e.g., a tungsten film and asilicon oxide film, and an organic resin film of polyimide or the likeformed over a substrate. Examples of a substrate to which alight-emitting element or a transistor is transferred include, inaddition to the above-described substrates over which a light-emittingelement or a transistor can be formed, a paper substrate, a cellophanesubstrate, an aramid film substrate, a polyimide film substrate, a stonesubstrate, a wood substrate, a cloth substrate (including a naturalfiber (e.g., silk, cotton, or hemp), a synthetic fiber (e.g., nylon,polyurethane, or polyester), a regenerated fiber (e.g., acetate, cupra,rayon, or regenerated polyester), or the like), a leather substrate, anda rubber substrate. With the use of any of these substrates, an increasein durability or heat resistance and a reduction in weight or thicknesscan be achieved.

A first reflective electrode 513B is electrically connected to thesource electrode or the drain electrode of the transistor 510, a secondreflective electrode 513G is electrically connected to the sourceelectrode or the drain electrode of the transistor 511, and a thirdreflective electrode 513R is electrically connected to the sourceelectrode or the drain electrode of the transistor 512.

A partition wall 520 is formed so as to cover end portions of the firstreflective electrode 513B, the second reflective electrode 513G, and thethird reflective electrode 513R. The partition wall 520 preferably has acurved surface with curvature at its upper end portion or lower endportion. With the partition wall 520 having such a shape, the coveragewith a film to be formed over the partition wall 520 can be favorable.

The first reflective electrode 513B serves as part of a lower electrodeof a first light-emitting element 524B. The second reflective electrode513G serves as part of a lower electrode of a second light-emittingelement 524G. The third reflective electrode 513R serves as part of alower electrode of a third light-emitting element 524R.

The first light-emitting element 524B, the second light-emitting element524G, and the third light-emitting element 524R can each have any of theelement structures described in Embodiment 1. With any of the elementstructures described in Embodiment 1, a light-emitting device with ahigh emission efficiency and a low power consumption can be provided.

Light is emitted from the first light-emitting element 524B, the secondlight-emitting element 524G, and the third light-emitting element 524Rthrough the second substrate 506. Therefore, the second substrate 506needs to have a light-transmitting property. For example, a materialsuch as a glass plate, a plastic plate, a polyester film, or an acrylicfilm can be used for the second substrate 506.

The second substrate 506 may be provided with an optical film such as apolarizing plate, a circularly polarizing plate (including anelliptically polarizing plate), or a retardation plate (a quarter-waveplate or a half-wave plate). The polarizing plate or the circularlypolarizing plate may be provided with an anti-reflective film. Forexample, anti-glare treatment by which reflected light can be diffusedby projections and depressions on the surface so as to reduce the glarecan be performed.

A protective film may be formed over the first light-emitting element524B, the second light-emitting element 524G, and the thirdlight-emitting element 524R. The protective film has a function ofpreventing oxygen, hydrogen, moisture, carbon dioxide, or the like fromentering each light-emitting element. For example, a silicon nitridefilm, a silicon nitride oxide film, an aluminum oxide film, or the likecan be used for the protective film.

This embodiment can be implemented in an appropriate combination withany of the structures described in the other embodiments.

Embodiment 3

In this embodiment, a display device including a light-emitting deviceaccording to one embodiment of the present invention will be describedwith reference to FIGS. 11A and 11B.

The display device illustrated in FIG. 11A includes a region includingpixels of display elements (the region is hereinafter referred to as apixel portion 602), a circuit portion provided outside the pixel portion602 and including a circuit for driving the pixels (the circuit portionis hereinafter referred to as a driver circuit portion 604), circuitseach having a function of protecting an element (the circuits arehereinafter referred to as protection circuits 606), and a terminalportion 607. Note that the protection circuits 606 are not necessarilyprovided.

Part of or the entire driver circuit portion 604 is preferably formedover a substrate over which the pixel portion 602 is formed. In thisway, the number of components and the number of terminals can bereduced. When part of or the entire driver circuit portion 604 is notformed over the substrate over which the pixel portion 602 is formed,part of or the entire driver circuit portion 604 can be mounted by COGor tape automated bonding (TAB).

The pixel portion 602 includes circuits for driving a plurality ofdisplay elements arranged in X (X is a natural number of greater than orequal to 2) rows and Y (Y is a natural number of greater than or equalto 2) columns (the circuits are hereinafter referred to as pixelcircuits 601). The driver circuit portion 604 includes driver circuitssuch as a circuit for supplying a signal (scan signal) to select a pixel(the circuit is hereinafter referred to as a scan line driver circuitportion 604 a) and a circuit for supplying a signal (data signal) todrive a display element in a pixel (the circuit is hereinafter referredto as a signal line driver circuit portion 604 b).

The scan line driver circuit portion 604 a includes a shift register orthe like. Through the terminal portion 607, the scan line driver circuitportion 604 a receives a signal for driving the shift register andoutputs a signal. For example, the scan line driver circuit portion 604a receives a start pulse signal, a clock signal, or the like and outputsa pulse signal. The scan line driver circuit portion 604 a has afunction of controlling potentials of wirings supplied with scan signals(the wirings are hereinafter referred to as scan lines GL_1 to GL_X). Aplurality of scan line driver circuit portions 604 a may be provided tocontrol the scan lines GL_1 to GL_X separately. Alternatively, the scanline driver circuit portion 604 a has a function of supplying aninitialization signal. However, without being limited thereto, the scanline driver circuit portion 604 a can supply other signals.

The signal line driver circuit portion 604 b includes a shift registeror the like. Through the terminal portion 607, the signal line drivercircuit portion 604 b receives a signal (image signal) from which a datasignal is derived, as well as a signal for driving the shift register.The signal line driver circuit portion 604 b has a function ofgenerating data signals written to the pixel circuits 601 based on imagesignals. The signal line driver circuit portion 604 b has a function ofcontrolling output of a data signal in response to a pulse signalproduced by input of a start pulse, a clock signal, or the like. Thesignal line driver circuit portion 604 b has a function of controllingpotentials of wirings supplied with data signals (the wirings arehereinafter referred to as data lines DL_1 to DL_). Alternatively, thesignal line driver circuit portion 604 b has a function of supplying aninitialization signal. However, without being limited thereto, thesignal line driver circuit portion 604 b can supply other signals.

The signal line driver circuit portion 604 b includes a plurality ofanalog switches, for example. The signal line driver circuit portion 604b can output, as the data signals, signals obtained by time-dividing theimage signals by sequentially turning on the plurality of analogswitches.

A pulse signal and a data signal are input to each of the plurality ofpixel circuits 601 through one of the plurality of scan lines GLsupplied with scan signals and one of the plurality of data lines DLsupplied with data signals, respectively. Writing and holding of thedata signal in each of the plurality of pixel circuits 601 arecontrolled by the scan line driver circuit portion 604 a. For example,to the pixel circuit 601 in m-th row and n-th column (m is a naturalnumber of less than or equal to X and n is a natural number of less thanor equal to Y), a pulse signal is input from the scan line drivercircuit portion 604 a through a scan line GL_m, and a data signal isinput from the signal line driver circuit portion 604 b through a dataline DL_n depending on the potential of the scan line GL_m.

In FIG. 11A, the protection circuit 606 is connected to, for example,the scan line GL between the scan line driver circuit portion 604 a andthe pixel portion 602. In addition, the protection circuit 606 isconnected to the data line DL between the signal line driver circuitportion 604 b and the pixel portion 602. In addition, the protectioncircuit 606 can be connected to a wiring between the scan line drivercircuit portion 604 a and the terminal portion 607. In addition, theprotection circuit 606 can be connected to a wiring between the signalline driver circuit portion 604 b and the terminal portion 607. Notethat the terminal portion 607 refers to a portion having terminals forinputting power, control signals, and image signals to the displaydevice from external circuits.

The protection circuit 606 is a circuit which electrically connects awiring connected to the protection circuit to another wiring when apotential out of a certain range is supplied to the wiring connected tothe protection circuit.

As illustrated in FIG. 11A, when the pixel portion 602 and the drivercircuit portion 604 are both provided with the protection circuits 606,the resistance of the display device to overcurrent generated byelectrostatic discharge (ESD) or the like can be improved. Theconfiguration of the protection circuits 606 is not limited thereto; forexample, the protection circuit 606 may be connected to the scan linedriver portion 604 a or the protection circuit 606 may be connected tothe signal line driver circuit portion 604 b. Alternatively, theprotection circuit 606 may be connected to the terminal portion 607.

FIG. 11A illustrates an example in which the driver circuit portion 604includes the scan line driver circuit portion 604 a and the signal linedriver circuit portion 604 b; however, the structure is not limitedthereto. For example, only the scan line driver circuit portion 604 amay be formed, and a separately prepared substrate over which a sourcedriver circuit is formed (e.g., a driver circuit substrate formed usinga single crystal semiconductor film or a polycrystalline semiconductorfilm) may be mounted.

Each of the plurality of pixel circuits 601 illustrated in FIG. 11A canhave a structure illustrated in FIG. 11B, for example.

The pixel circuit 601 illustrated in FIG. 11R includes transistors 652and 654, a capacitor 662, and a light-emitting element 672.

One of a source electrode and a drain electrode of the transistor 652 iselectrically connected to a wiring supplied with a data signal(hereinafter referred to as a data line DL_n). A gate electrode of thetransistor 652 is electrically connected to a wiring supplied with agate signal (hereinafter referred to as a scan line GL_m).

The transistor 652 has a function of controlling whether to write a datasignal by being turned on or off.

One of a pair of electrodes of the capacitor 662 is electricallyconnected to a wiring supplied with a potential (hereinafter referred toas a potential supply line VL_a), and the other is electricallyconnected to the other of the source electrode and the drain electrodeof the transistor 652.

The capacitor 662 functions as a storage capacitor for holding writtendata.

One of a source electrode and a drain electrode of the transistor 654 iselectrically connected to the potential supply line VL_a. A gateelectrode of the transistor 654 is electrically connected to the otherof the source electrode and the drain electrode of the transistor 652.

One of an anode and a cathode of the light-emitting element 672 iselectrically connected to a potential supply line VL_b, and the other iselectrically connected to the other of the source electrode and thedrain electrode of the transistor 654.

As the light-emitting element 672, any of the light-emitting elementsdescribed in Embodiment 1 can be used.

A high power supply potential VDD is supplied to one of the potentialsupply line VL_a and the potential supply line VL_b, and a low powersupply potential VSS is supplied to the other.

For example, in the display device including the pixel circuit 601 inFIG. 11B, the pixel circuits 601 are sequentially selected row by row bythe scan line driver circuit portion 604 a illustrated in FIG. 11A,whereby the transistors 652 are turned on and data signals are written.

When the transistors 652 are turned off, the pixel circuits 601 in whichthe data signals have been written are brought into a holding state. Theamount of current flowing between the source electrode and the drainelectrode of the transistor 654 is controlled in accordance with thepotential of the written data signal. The light-emitting element 672emits light with a luminance corresponding to the amount of the flowingcurrent. This operation is sequentially performed row by row; thus, animage can be displayed.

The structure described in this embodiment can be used in an appropriatecombination with any of the structures described in the otherembodiments.

Embodiment 4

In this embodiment, a display module and electronic devices eachincluding a light-emitting device according to one embodiment of thepresent invention will be described with reference to FIG. 12 and FIGS.13A to 13G.

In a display module 8000 illustrated in FIG. 12, a touch panel 8004connected to an FPC 8003, a display panel 8006 connected to an FPC 8005,a frame 8009, a printed board 8010, and a battery 8011 are providedbetween an upper cover 8001 and a lower cover 8002.

A light-emitting device according to one embodiment of the presentinvention can be used for the display panel 8006, for example.

The shapes and sizes of the upper cover 8001 and the lower cover 8002can be changed as appropriate in accordance with the sizes of the touchpanel 8004 and the display panel 8006.

The touch panel 8004 can be a resistive touch panel or a capacitivetouch panel and can be provided so as to overlap with the display panel8006. Alternatively, a counter substrate (sealing substrate) of thedisplay panel 8006 can have a touch panel function. Alternatively, aphotosensor may be provided in each pixel of the display panel 8006 toform an optical touch panel.

The frame 8009 protects the display panel 8006 and also functions as anelectromagnetic shield for blocking electromagnetic waves generated bythe operation of the printed board 8010. The frame 8009 can alsofunction as a radiator plate.

The printed board 8010 is provided with a power supply circuit and asignal processing circuit for outputting a video signal and a clocksignal. As a power source for supplying power to the power supplycircuit, an external commercial power source or a power source using thebattery 8011 provided separately may be used. The battery 8011 can beomitted in the case of using a commercial power source.

The display module 8000 may be additionally provided with a member suchas a polarizing plate, a retardation plate, or a prism sheet.

FIGS. 13A to 13G illustrate electronic devices. These electronic devicescan each include a housing 9000, a display portion 9001, a speaker 9003,an operation key 9005 (including a power switch or an operation switch),a connection terminal 9006, a sensor 9007 (a sensor having a function ofmeasuring force, displacement, position, speed, acceleration, angularvelocity, rotational frequency, distance, light, liquid, magnetism,temperature, chemical substance, sound, time, hardness, electric field,current, voltage, power, radiation, flow rate, humidity, gradient,oscillation, odor, or infrared rays), a microphone 9008, and the like.

The electronic devices illustrated in FIGS. 13A to 13G can have avariety of functions, for example, a function of displaying a variety ofinformation (a still image, a moving image, a text image, and the like)on the display portion, a touch sensor function, a function ofdisplaying a calendar, the date, the time, and the like, a function ofcontrolling processing with a variety of software (programs), a wirelesscommunication function, a function of being connected to a variety ofcomputer networks with a wireless communication function, a function oftransmitting and receiving a variety of data with a wirelesscommunication function, a function of reading a program or data storedin a storage medium and displaying the program or data on the displayportion, and the like. Note that functions of the electronic devicesillustrated in FIGS. 13A to 13G are not limited thereto, and theelectronic devices can have a variety of functions. Although notillustrated in FIGS. 13A to 13G, the electronic devices may each have aplurality of display portions. The electronic devices may each have acamera or the like and a function of taking a still image, a function oftaking a moving image, a function of storing the taken image in astorage medium (an external storage medium or a storage mediumincorporated in the camera), a function of displaying the taken image onthe display portion, and the like.

The electronic devices illustrated in FIGS. 13A to 13G will be describedin detail below.

FIG. 13A is a perspective view of a portable information terminal 9100.The display portion 9001 of the portable information terminal 9100 isflexible and thus can be incorporated along the curved surface of thehousing 9000. Furthermore, the display portion 9001 includes a touchsensor, and operation can be performed by touching a screen with afinger, a stylus, or the like. For example, by touching an icondisplayed on the display portion 9001, an application can be started.

FIG. 13B is a perspective view of a portable information terminal 9101.The portable information terminal 9101 functions as, for example, one ormore of a telephone set, a notebook, an information browsing system, andthe like. Specifically, the portable information terminal 9101 can beused as a smartphone. Note that the speaker 9003, the connectionterminal 9006, the sensor 9007, and the like, which are not illustratedin FIG. 13B, can be positioned in the portable information terminal 9101as in the portable information terminal 9100 illustrated in FIG. 13A.The portable information terminal 9101 can display characters and imageinformation on its plurality of surfaces. For example, three operationbuttons 9050 (also referred to as operation icons, or simply, icons) canbe displayed on one surface of the display portion 9001. Furthermore,information 9051 indicated by dashed rectangles can be displayed onanother surface of the display portion 9001. Examples of the information9051 include notification from a social networking service (SNS),display indicating reception of an e-mail or an incoming call, the titleof the e-mail, the SNS, or the like, the sender of the e-mail, the SNS,or the like, the date, the time, remaining battery, and the receptionstrength of an antenna. Instead of the information 9051, the operationbuttons 9050 or the like may be displayed in the position where theinformation 9051 is displayed.

FIG. 13C is a perspective view of a portable information terminal 9102.The portable information terminal 9102 has a function of displayinginformation on three or more surfaces of the display portion 9001. Here,information 9052, information 9053, and information 9054 are displayedon different surfaces. For example, a user of the portable informationterminal 9102 can see the display (here, the information 9053) with theportable information terminal 9102 put in a breast pocket of his/herclothes. Specifically, a caller's phone number, name, or the like of anincoming call is displayed in the position that can be seen from abovethe portable information terminal 9102. Thus, the user can see thedisplay without taking out the portable information terminal 9102 fromthe pocket and decide whether to answer the call.

FIG. 13D is a perspective view of a watch-type portable informationterminal 9200. The portable information terminal 9200 is capable ofexecuting a variety of applications such as mobile phone calls,e-mailing, viewing and editing texts, music reproduction, Internetcommunication, and computer games. The display surface of the displayportion 9001 is curved, and images can be displayed on the curveddisplay surface. The portable information terminal 9200 can employ nearfield communication conformable to a communication standard. Forexample, hands-free calling can be achieved with mutual communicationbetween the portable information terminal 9200 and a headset capable ofwireless communication. Moreover, the portable information terminal 9200includes the connection terminal 9006, and data can be directlytransmitted to and received from another information terminal via aconnector. Charging through the connection terminal 9006 is alsopossible. Note that the charging operation may be performed by wirelesspower feeding without using the connection terminal 9006.

FIGS. 13E, 13F, and 13G are perspective views of a foldable portableinformation terminal 9201 that is opened, that is shifted from theopened state to the folded state or from the folded state to the openedstate, and that is folded, respectively. The portable informationterminal 9201 is highly portable when folded. When the portableinformation terminal 9201 is opened, a seamless large display regionprovides high browsability. The display portion 9001 of the portableinformation terminal 9201 is supported by three housings 9000 joinedtogether by hinges 9055. By folding the portable information terminal9201 at a connection portion between two housings 9000 with the hinges9055, the portable information terminal 9201 can be reversibly changedin shape from the opened state to the folded state. For example, theportable information terminal 9201 can be bent with a radius ofcurvature of greater than or equal to 1 mm and less than or equal to 150mm.

The electronic devices described in this embodiment each include thedisplay portion for displaying some kinds of information. However, alight-emitting device according to one embodiment of the presentinvention can also be used for an electronic device that does notinclude a display portion. Furthermore, the display portions of theelectronic devices described in this embodiment may also be non-flexibleand can display images on a flat surface without limitation to aflexible mode capable of displaying images on a curved display surfaceor a foldable mode.

The structure described in this embodiment can be used in an appropriatecombination with any of the structures described in the otherembodiments.

Embodiment 5

In this embodiment, examples of a lighting device to which alight-emitting device according to one embodiment of the presentinvention is applied will be described with reference to FIG. 14.

FIG. 14 illustrates an example in which a light-emitting device is usedfor an indoor lighting device 8501. Since the area of the light-emittingdevice can be increased, a lighting device having a large area can beformed. In addition, a lighting device 8502 in which a light-emittingregion has a curved surface can be obtained with the use of a housingwith a curved surface. A light-emitting element included in thelight-emitting device described in this embodiment is in the form of athin film, which allows the housing to be designed more freely.Therefore, the lighting device can be elaborately designed in a varietyof ways. Furthermore, a wall of the room may be provided with alarge-sized lighting device 8503. Touch sensors may be provided in thelighting devices 8501, 8502, and 8503 to control the power on/off of thelighting devices.

When the light-emitting device is used for a surface of a table, alighting device 8504 that has a function as a table can be obtained.When the light-emitting device is used as part of other furniture, alighting device which has a function as the furniture can be obtained.

In this manner, a variety of lighting devices to which thelight-emitting device is applied can be obtained. Note that suchlighting devices are also embodiments of the present invention.

The structure described in this embodiment can be used in an appropriatecombination with any of the structures described in the otherembodiments.

Example 1

In this example, a light-emitting element 1 (referred to as LEE 1 in thedrawings) and a light-emitting element 2 (referred to as LEE 2 in thedrawings) which are embodiments of the present invention and a referencelight-emitting element 3 (referred to as LEE 3 in the drawings) werefabricated and evaluated. The element structures of the light-emittingelement 1, the light-emitting element 2, and the referencelight-emitting element 3 will be described in detail with reference toFIG. 15. First, chemical formulae of materials used for thelight-emitting elements in this example are shown below.

A method for fabricating the light-emitting element 1, thelight-emitting element 2, and the reference light-emitting element 3 ofthis example will be described below.

<<Method for Fabricating Light-Emitting Element 1, Light-EmittingElement 2, and Reference Light-Emitting Element 3>>

First, over a substrate 4002, an alloy film of silver (Ag), palladium(Pd), and copper (Cu) (the alloy film is hereinafter referred to as APC)was formed as a reflective electrode 4004 by a sputtering method. Notethat the thickness of the reflective electrode 4004 was 100 nm and thearea was 4 mm² (2 mm×2 mm).

Then, over the reflective electrode 4004, a film of indium tin oxidecontaining silicon oxide (the film is hereinafter referred to as ITSO)was formed as a transparent conductive film 4006 by a sputtering method.Note that the thickness of the transparent conductive film 4006 was 60nm in the light-emitting element 1, the thickness of the transparentconductive film 4006 was 30 nm in the light-emitting element 2, and thethickness of the transparent conductive film 4006 was 10 nm in thereference light-emitting element 3.

Then, as pretreatment of evaporation of an organic compound layer, thetransparent conductive film 4006 side of the substrate 4002 providedwith the reflective electrode 4004 and the transparent conductive film4006 was washed with water, baking was performed at 200° C. for onehour, and then UV ozone treatment was performed on a surface of thetransparent conductive film 4006 for 370 seconds.

After that, the substrate 4002 was transferred into a vacuum evaporationapparatus in which the pressure had been reduced to approximately 10⁻⁴Pa, and was subjected to vacuum baking at 170° C. for 60 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate 4002 was cooled down for about 30 minutes.

Then, the substrate 4002 was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate 4002 over whichthe transparent conductive film 4006 was formed faced downward. In thisexample, by a vacuum evaporation method, a first hole-injection layer4131, a first hole-transport layer 4132, a first light-emitting layer4008, first electron-transport layers 4133 a and 4133 b, a firstelectron-injection layer 4134, a charge-generation layer 4010, a secondhole-injection layer 4135, a second hole-transport layer 4136, secondlight-emitting layers 4012 a and 4012 b, second electron-transportlayers 4137 a and 4137 b, and a second electron-injection layer 4138were sequentially formed. The fabrication method will be described indetail below.

First, the pressure in the vacuum evaporation apparatus was reduced to10⁻⁴ Pa. Then, on the transparent conductive film 4006,3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn)and molybdenum oxide were co-evaporated as the first hole-injectionlayer 4131 so that the mass ratio of PcPPn to molybdenum oxide was1:0.5. Note that the thickness of the first hole-injection layer 4131was 35 nm in each of the light-emitting element 1 and the light-emittingelement 2, and the thickness of the first hole-injection layer 4131 was15 nm in the reference light-emitting element 3.

Then, the first hole-transport layer 4132 was formed on the firsthole-injection layer 4131. As the first hole-transport layer 4132, PCPPnwas evaporated. Note that the thickness of the first hole-transportlayer 4132 was 15 nm in each of the light-emitting element 1 and thelight-emitting element 2, and the thickness of the first hole-transportlayer 4132 was 10 nm in the reference light-emitting element 3.

Then, the first light-emitting layer 4008 was formed on the firsthole-transport layer 4132. As the first light-emitting layer 4008,9-[4-(0-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA)and N,N′-bis(dibenzofuran-4-yl)-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6FrAPrn-II) were co-evaporated so that the mass ratioof CzPA to 1,6FrAPrn-II was 1:0.05. The thickness of the firstlight-emitting layer 4008 was 25 nm.

Then, on the first light-emitting layer 4008, CzPA was evaporated to athickness of 5 nm as the first electron-transport layer 4133 a. Then, onthe first electron-transport layer 4133 a, bathophenanthroline(abbreviation: Bphen) was evaporated to a thickness of 15 nm as thefirst electron-transport layer 4133 b. Then, on the firstelectron-transport layer 4133 b, lithium oxide (Li₂O) was evaporated toa thickness of 0.1 nm as the first electron-injection layer 4134.

Then, on the first electron-injection layer 4134, copper phthalocyanine(abbreviation: CuPc) was evaporated to a thickness of 2 nm as thecharge-generation layer 4010.

Then, on the charge-generation layer 4010,1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) andmolybdenum oxide were co-evaporated as the second hole-injection layer4135 so that the mass ratio of DBT3P-II to molybdenum oxide was 10.5.Note that the thickness of the second hole-injection layer 4135 was 12.5nm.

Then, on the second hole-injection layer 4135, BPAFLP was evaporated toa thickness of 20 nm as the second hole-transport layer 4136.

Then, on the second hole-transport layer 4136,2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB), and(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: Ir(tBuppm)₂(acac)) were co-evaporated as the secondlight-emitting layer 4012 a so that the mass ratio of 2mDBTBPDBq-II toPCBNBB and Ir(tBuppm)₂(acac) was 0.7:03:0.06. Note that the thickness ofthe second light-emitting layer 4012 a was 20 ran.

Then, on the second light-emitting layer 4012 a, 2mDBTBPDBq-II andbis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,4-pentanedionato-κ²O,O′)iridium(II) (abbreviation:Ir(dmdppr-dmp)₂(acac)) were co-evaporated as the second light-emittinglayer 4012 b so that the mass ratio of 2mDBTBPDBq-II toIr(dmdppr-dmp)₂(acac) was 1:0.06. Note that the thickness of the secondlight-emitting layer 4012 b was 20 nm.

Then, on the second light-emitting layer 4012 b,2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II) was evaporated to a thickness of 30 nm as the secondelectron-transport layer 4137 a. Then, on the second electron-transportlayer 4137 a, Bphen was evaporated to a thickness of 15 nm as the secondelectron-transport layer 4137 b.

Then, on the second electron-transport layer 4137 b, lithium fluoride(LiF) was evaporated to a thickness of 1 nm as the secondelectron-injection layer 4138.

Then, on the second electron-injection layer 4138, silver (Ag) andmagnesium (Mg) were co-evaporated as a semi-transmissive andsemi-reflective electrode 4014 a so that the volume ratio was 1:0.1.Note that the thickness of the semi-transmissive and semi-reflectiveelectrode 4014 a was 15 nm. Then, on the semi-transmissive andsemi-reflective electrode 4014 a, a film of indium tin oxide (ITO) witha thickness of 70 nm was formed by a sputtering method as asemi-transmissive and semi-reflective electrode 4014 b.

In all of the above evaporation steps, evaporation was performed by aresistance-heating method.

Table 1 shows the element structures of the light-emitting element 1,the light-emitting element 2, and the reference light-emitting element 3fabricated as described above.

TABLE 1 Reflective Transparent First Hole- First Hole- First Light-First Electron- Electrode Conductive Film injection Layer transportLayer emitting Layer transport Layer Light- APC ITSO PCPPn:MoOx PCPPn*1) CzPA BPhen emitting (100 nm) (60 nm) (1:0.5) (15 nm) (5 nm) (15 nm)Element 1 (35 nm) Light- ITSO PCPPn:MoOx PCPPn emitting (30 nm) (1:0.5)(15 nm) Element 2 (35 nm) Rerence Light- ITSO PCPPn:MoOx PCPPn emitting(10 nm) (1:05) (10 nm) Element 3 (15 nm) First Electron- Charge- SecondHole- Second Hole- Second Light- injection Layer generation Layerinjection Layer transport Layer emitting Layer Li₂O CuPc DBT3P-II:MoOxBPAFLP *2) *3) (0.1 nm) (2 nm) (1:0.5) (20 nm) (12.5 nm) SecondElectron- Second Electron- Semi-transmissive and Coloring transportLayer injection Layer Semi-reflective Electrode Layer 2mDBTBPDBq-IIBphen LiF Ag:Mg ITO Red (30 nm) (15 nm) (1 nm) (1:0.1) (70 nm) 2.4 μm(15 nm) Green 1.3 μm Blue 0.6 μm *1) CzPA:1,6FrAPrn-II(1:0.05)(25 nm)*2) 2mDBTBPDBq-II:PCBNBB:Ir(tBuppm)₂(acac) (0.7:0.3:0.06) (20 nm) *3)2mDBTBPDBq-II:Ir(dmdppr-dmp)₂(acac) (1:0.06) (20 nm)

As shown in Table 1, a red color filter (R) with a thickness of 2.4 μmwas formed as a coloring layer 4156 on a counter substrate 4152 in thelight-emitting element 1, a green color filter (G) with a thickness of1.3 μm was formed as the coloring layer 4156 on the counter substrate4152 in the light-emitting element 2, and a blue color filter (B) with athickness of 0.6 μm was formed as the coloring layer 4156 on the countersubstrate 4152 in the reference light-emitting element 3.

Each of the light-emitting element 1, the light-emitting element 2, andthe reference light-emitting element 3 fabricated as described above wassealed by being bonded to the counter substrate 4152 fabricated asdescribed above in a glove box in a nitrogen atmosphere so as not to beexposed to the air (specifically, a sealant was applied to surround theelement, and irradiation with ultraviolet light having a wavelength of365 nm at 6 J/cm² and heat treatment at 80° C. for 1 hour were performedfor sealing).

<<Operation Characteristics of Light-Emitting Element 1, Light-EmittingElement 2, and Reference Light-Emitting Element 3>>

Operation characteristics of the light-emitting element 1, thelight-emitting element 2, and the reference light-emitting element 3fabricated as described above were measured. Note that measurements wereperformed at room temperature (in an atmosphere kept at 25° C.).

FIG. 16A shows current efficiency-luminance characteristics of thelight-emitting element 1, the light-emitting element 2, and thereference light-emitting element 3. In FIG. 16A, the vertical axisrepresents current efficiency (cd/A) and the horizontal axis representsluminance (cd/m²). FIG. 16B shows current-voltage characteristics of thelight-emitting element 1, the light-emitting element 2, and thereference light-emitting element 3. In FIG. 16B, the vertical axisrepresents current (mA) and the horizontal axis represents voltage (V).FIG. 17 shows luminance-voltage characteristics of the light-emittingelement 1, the light-emitting element 2, and the referencelight-emitting element 3. In FIG. 17, the vertical axis representsluminance (cd/m²) and the horizontal axis represents voltage (V).

Table 2 shows initial values of main characteristics of thelight-emitting element 1, the light-emitting element 2, and thereference light-emitting element 3 at a luminance of about 1000 cd/m².

TABLE 2 Voltage Current Current Density Chromaticity Luminance CurrentEfficiency (V) (mA) (mA/cm²) (x, y) (cd/m²) (cd/A) Light- 6.6 0.15 3.9(0.67, 0.33) 903 23.0 emitting Element 1 Light- 6.2 0.07 1.7 (0.28,0.71) 1193 68.8 emitting Element 2 Reference Light- 8.8 1.59 39.7 (0.14,0.06) 1086 2.7 emitting Element 3

FIG. 18 shows the emission spectra of the light-emitting element 1, thelight-emitting element 2, and the reference light-emitting element 3through which current flows at a current density of 2.5 mA/cm². As shownin FIG. 18, the emission spectrum of the light-emitting element 1 has apeak at around 611 nm, the emission spectrum of the light-emittingelement 2 has a peak at around 539 nm, and the emission spectrum of thereference light-emitting element 3 has a peak at around 460 nm.

The above results suggest that the light-emitting element 1 emits redlight (R), the light-emitting element 2 emits green light (G), and thereference light-emitting element 3 emits blue light (B); thus, by usingthe light-emitting element 1, the light-emitting element 2, and thereference light-emitting element 3 in combination, full-color displaycan be achieved. However, when the reference light-emitting element 3was compared with the light-emitting elements 1 and 2 (although theycannot be simply compared with each other because the element structuresand the emission wavelengths were different from each other), thecurrent efficiency of the reference light-emitting element 3 was lowerthan those of the light-emitting elements 1 and 2.

Example 2

In this example, a light-emitting element 4 (referred to as LEE 4 in thedrawings) and a light-emitting element 5 (referred to as LEE 5 in thedrawings) which are embodiments of the present invention were fabricatedand evaluated. The element structures of the light-emitting element 4and the light-emitting element 5 will be described in detail withreference to FIG. 15. The light-emitting element 4 and thelight-emitting element 5 in this example were fabricated by using thesame materials as those of the light-emitting elements in Example 1.Therefore, description of chemical formulae of materials used in thisexample is omitted.

<<Method for Fabricating Light-Emitting Element 4 and Light-EmittingElement 5>>

First, over the substrate 4002, APC was formed as the reflectiveelectrode 4004 by a sputtering method. Note that the thickness of thereflective electrode 4004 was 100 nm and the area was 4 mm² (2 mm×2 mm).

Then, over the reflective electrode 4004, ITSO was formed as thetransparent conductive film 4006 by a sputtering method. Note that thethickness of the transparent conductive film 4006 was 60 nm in each ofthe light-emitting element 4 and the light-emitting element 5.

Then, as pretreatment of evaporation of an organic compound layer, thetransparent conductive film 4006 side of the substrate 4002 providedwith the reflective electrode 4004 and the transparent conductive film4006 was washed with water, baking was performed at 200° C. for onehour, and then UV ozone treatment was performed on a surface of thetransparent conductive film 4006 for 370 seconds.

After that, the substrate 4002 was transferred into a vacuum evaporationapparatus in which the pressure had been reduced to approximately 10⁻⁴Pa, and was subjected to vacuum baking at 170° C. for 60 minutes in aheating chamber of the vacuum evaporation apparatus, and then thesubstrate 4002 was cooled down for about 30 minutes.

Then, the substrate 4002 was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate 4002 over whichthe transparent conductive film 4006 was formed faced downward. In thisexample, by a vacuum evaporation method, the first hole-injection layer4131, the first hole-transport layer 4132, the first light-emittinglayer 4008, the first electron-transport layers 4133 a and 4133 b, thefirst electron-injection layer 4134, the charge-generation layer 4010,the second hole-injection layer 4135, the second hole-transport layer4136, the second light-emitting layers 4012 a and 4012 b, the secondelectron-transport layers 4137 a and 4137 b, and the secondelectron-injection layer 4138 were sequentially formed. The fabricationmethod will be described in detail below.

First, the pressure in the vacuum evaporation apparatus was reduced to10⁻⁴ Pa. Then, on the transparent conductive film 4006, PCPPn andmolybdenum oxide were co-evaporated as the first hole-injection layer4131 so that the mass ratio of PcPPn to molybdenum oxide was 1:0.5. Notethat the thickness of the first hole-injection layer 4131 was 65 nm inthe light-emitting element 4, and the thickness of the firsthole-injection layer 4131 was 70 nm in the light-emitting element 5.

Then, the first hole-transport layer 4132 was formed on the firsthole-injection layer 4131. As the first hole-transport layer 4132, PCPPnwas evaporated. Note that the thickness of the first hole-transportlayer 4132 was 15 n in each of the light-emitting element 4 and thelight-emitting element 5.

Then, the first light-emitting layer 4008 was formed on the firsthole-transport layer 4132. As the first light-emitting layer 4008, CzPAand 1,6FrAPrn-II were co-evaporated so that the mass ratio of CzPA to1,6FrAPrn-II was 1:0.05. The thickness of the first light-emitting layer4008 was 25 nm.

Then, on the first light-emitting layer 4008, CzPA was evaporated to athickness of 5 nm as the first electron-transport layer 4133 a. Then, onthe first electron-transport layer 4133 a, Bphen was evaporated to athickness of 15 nm as the first electron-transport layer 4133 b. Then,on the first electron-transport layer 4133 b, Li₂O was evaporated to athickness of 0.1 nm as the first electron-injection layer 4134.

Then, on the first electron-injection layer 4134, CuPc was evaporated toa thickness of 2 nm as the charge-generation layer 4010.

Then, on the charge-generation layer 4010, DBT3P-II and molybdenum oxidewere co-evaporated as the second hole-injection layer 4135 so that themass ratio of DBT3P-II to molybdenum oxide was 1:0.5. Note that thethickness of the second hole-injection layer 4135 was 12.5 nm.

Then, on the second hole-injection layer 4135, BPAFLP was evaporated toa thickness of 20 nm as the second hole-transport layer 4136.

Then, on the second hole-transport layer 4136, 2mDBTBPDBq-II, PCBNBB,and Ir(tBuppm)₂(acac) were co-evaporated as the second light-emittinglayer 4012 a so that the mass ratio of 2mDBTBPDBq-II to PCBNBB andIr(tBuppm)₂(acac) was 0.7:03:0.06. Note that the thickness of the secondlight-emitting layer 4012 a was 20 nm.

Then, on the second light-emitting layer 4012 a, 2mDBTBPDBq-II andIr(dmdppr-dmp)₂(acac) were co-evaporated as the second light-emittinglayer 4012 b so that the mass ratio of 2mDBTBPDBq-II toIr(dmdppr-dmp)₂(acac) was 1:0.06. Note that the thickness of the secondlight-emitting layer 4012 b was 20 nm.

Then, on the second light-emitting layer 4012 b, 2mDBTPDBq-II wasevaporated to a thickness of 30 nm as the second electron-transportlayer 4137 a. Then, on the second electron-transport layer 4137 a, Bphenwas evaporated to a thickness of 15 nm as the second electron-transportlayer 4137 b.

Then, on the second electron-transport layer 4137, LiF was evaporated toa thickness of 1 nm as the second electron-injection layer 4138.

Then, on the second electron-injection layer 4138, silver (Ag) andmagnesium (Mg) were co-evaporated as the semi-transmissive andsemi-reflective electrode 4014 a so that the volume ratio was 1:0.1.Note that the thickness of the semi-transmissive and semi-reflectiveelectrode 4014 a was 15 nm. Then, on the semi-transmissive andsemi-reflective electrode 4014 a, a film of ITO with a thickness of 70nm was formed by a sputtering method as the semi-transmissive andsemi-reflective electrode 4014 b.

In all of the above evaporation steps, evaporation was performed by aresistance-heating method.

Table 3 shows the element structures of the light-emitting element 4 andthe light-emitting element 5 fabricated as described above.

TABLE 3 Reflective Transparent First Hole- First Hole- First Light-First Electron- Elektrode Conductive Film injection Layer transportLayer emitting Layer transport Layer Light- APC ITSO PCPPn:MoOx PCPPn*1) CzPA BPhen emitting (100 nm) (60 nm) (1:0.5) (15 nm) (5 nm) (15 nm)Element 4 (65 nm) Light- ITSO PCPPn:MoOx PCPPn emitting (60 nm) (1:0.5)(15 nm) Element 5 (70 nm) First Electron- Charge- Second Hole- SecondHole- Second Light- injection Layer generation Layer injection Layertransport Layer emitting Layer Li₂O CuPc DBT3P-II:MoOx BPAFLP *2) *3)(0.1 nm) (2 nm) (1:0.5) (20 nm) (12.5 nm) Second Electron- SecondElectron- Semi-transmissive and Coloring transport Layer injection LayerSemi-reflective Electrode Layer 2mDBTBPDBq-II Bphen LiF Ag:Mg ITO Blue(30 nm) (15 nm) (1 nm) (1:0.1) (70 nm) 0.6 μm (15 nm) Blue 1.0 μm *1)CzPA:1,6FrAPrn-II(1:0.05)(25 nm) *2)2mDBTBPDBq-II:PCBNBB:Ir(tBuppm)₂(acac) (0.7:0.3:0.06) (20 nm) *3)2mDBTBPDBq-II:Ir(dmdppr-dmp)₂(acac) (1:0.06) (20 nm)

As shown in Table 3, a blue color filter (B) with a thickness of 0.6 μmwas formed as the coloring layer 4156 on the counter substrate 4152 inthe light-emitting element 4, and a blue color filter (B) with athickness of 1.0 μm was formed as the coloring layer 4156 on the countersubstrate 4152 in the light-emitting element 5.

Each of the light-emitting element 4 and the light-emitting element 5fabricated as described above was sealed by being bonded to the countersubstrate 4152 fabricated as described above in a glove box in anitrogen atmosphere so as not to be exposed to the air (specifically, asealant was applied to surround the element, and irradiation withultraviolet light having a wavelength of 365 nm at 6 J/cm² and heattreatment at 80° C. for 1 hour were performed for sealing).

<<Operation Characteristics of Light-Emitting Element 4 andLight-Emitting Element 5>>

Operation characteristics of the light-emitting element 4 and thelight-emitting element 5 fabricated as described above were measured.Note that measurements were performed at room temperature (in anatmosphere kept at 25° C.).

FIG. 19A shows current efficiency-luminance characteristics of thelight-emitting element 4 and the light-emitting element 5. In FIG. 19A,the vertical axis represents current efficiency (cd/A) and thehorizontal axis represents luminance (cd/m²). FIG. 19B showscurrent-voltage characteristics of the light-emitting element 4 and thelight-emitting element 5. In FIG. 19B, the vertical axis representscurrent (mA) and the horizontal axis represents voltage (V). FIG. 20shows luminance-voltage characteristics of the light-emitting element 4and the light-emitting element 5. In FIG. 20, the vertical axisrepresents luminance (cd/m²) and the horizontal axis represents voltage(V). In FIGS. 19A and 19B and FIG. 20, the measurement results of thelight-emitting element 4 and the light-emitting element 5 aresubstantially the same.

Table 4 shows initial values of main characteristics of thelight-emitting element 4 and the light-emitting element 5 at a luminanceof about 1000 cd/m².

TABLE 4 Voltage Current Current Density Chromaticity Luminance CurrentEfficiency (V) (mA) (mA/cm²) (x, y) (cd/m²) (cd/A) Light- 8.2 0.98 24.4(0.16, 0.07) 1040 4.3 emitting Element 4 Licht- 8.4 1.19 29.9 (0.14,0.07) 1001 3.4 emitting Element 5

FIG. 21 shows the emission spectra of the light-emitting element 4 andthe light-emitting element 5 through which current flows at a currentdensity of 2.5 mA/cm². As shown in FIG. 21, the emission spectrum of thelight-emitting element 4 has a peak at around 462 nm, and the emissionspectrum of the light-emitting element 5 has a peak at around 466 nm.

The above results suggest that the light-emitting element 4 and thelight-emitting element 5 emit blue light (B) and that the currentefficiency of the light-emitting element 4 and the light-emittingelement 5 which are embodiments of the present invention is higher thanthat of the reference light-emitting element 3 fabricated in Example 1,which might be caused by a difference in optical path length between APCused as the reflective electrode and the first light-emitting layer.

Table 5 shows the following data: the optical path length between APCand the first light-emitting layer (hereinafter referred to as EML1 insome cases) of each of the light-emitting element 1, the light-emittingelement 2, and the reference light-emitting element 3 fabricated inExample 1, and the light-emitting element 4 and the light-emittingelement 5 fabricated in Example 2; the optical path length between APCand the second light-emitting layer (hereinafter referred to as EML2 insome cases) of each of the light-emitting elements; and ¼ and ¾ of thewavelength of light emitted from each of the light-emitting elements.

TABLE 5 Optical Path Length Optical Path Length between APC and betweenAPC and EML1 EML2 λ/4 3 λ/4 Light-emitting 275 454 153 458 Element 1Light-emitting 209 388 135 404 Element 2 Reference 117 297 115 345Light-emitting Element 3 Light-emitting 332 511 116 347 Element 4Light-emitting 341 521 117 350 Element 5 ※ λ represents wavelength oflight emitted from each light-emitting element.

The optical path length in Table 5 was calculated under the followingconditions: the refractive index of the ITSO film used as thetransparent conductive film 4006 was 2.2, and the reflective indices ofthe other organic layers (the first hole-injection layer 4131, the firsthole-transport layer 4132, the first light-emitting layer 4008, thefirst electron-transport layer 4133, the first electron-injection layer4134, the charge-generation layer 4010, the second hole-injection layer4135, the second hole-transport layer 4136, and the secondlight-emitting layer 4012) were 1.9.

It is suggested that, as shown in Table 5, because the optical pathlength between APC and EML1 was approximately λ_(B)/4 in the referencelight-emitting element 3, light was scattered or absorbed in thevicinity of a surface of APC, which led to a low current efficiency. Onthe other hand, it is suggested that because the optical path lengthbetween APC and EML1 was approximately 3λ_(B)/4 in each of thelight-emitting element 4 and the light-emitting element 5 which areembodiments of the present invention, scattering or absorption of lightin the vicinity of a surface of APC was suppressed, which led to ahigher current efficiency than in the reference light-emitting element3.

Table 5 also shows that the optical path length between APC and EML2 wasapproximately 3λ_(R)/4 in the light-emitting element 1 which is oneembodiment of the present invention and that the optical path lengthbetween APC and EML2 was approximately 3λ_(G)/4 in the light-emittingelement 2 which is one embodiment of the present invention.

The structures described in this example can be used in an appropriatecombination with any of the structures described in the otherembodiments and example.

This application is based on Japanese Patent Application serial no.2014-101116 filed with Japan Patent Office on May 15, 2014, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A light-emitting device comprising: a firstlight-emitting element being capable of emitting blue light, the firstlight-emitting element comprising: a first transparent conductive film;a first light-emitting layer over the first transparent conductive film;a second light-emitting layer over the first light-emitting layer; andan electrode over the second light-emitting layer, a secondlight-emitting element being capable of emitting green light, the secondlight-emitting element comprising: a second transparent conductive film;the first light-emitting layer over the second transparent conductivefilm; the second light-emitting layer over the first light-emittinglayer; and the electrode over the second light-emitting layer, a thirdlight-emitting element being capable of emitting red light, the thirdlight-emitting element comprising: a third transparent conductive film;the first light-emitting layer over the third transparent conductivefilm; the second light-emitting layer over the first light-emittinglayer; and the electrode over the second light-emitting layer, and afourth light-emitting element being capable of emitting white light, thefourth light-emitting element comprising: a fourth transparentconductive film; the first light-emitting layer over the fourthtransparent conductive film; the second light-emitting layer over thefirst light-emitting layer; and the electrode over the secondlight-emitting layer, wherein the first transparent conductive film hasa first region, wherein the second transparent conductive film has asecond region, wherein the third transparent conductive film has a thirdregion, wherein the fourth transparent conductive film has a fourthregion, wherein the first region is thicker than the third region andthe fourth region, and wherein each of the third region and the fourthregion is thicker than the second region.
 2. The light-emitting deviceaccording to claim 1, wherein the first light-emitting layer comprises afirst light-emitting substance emitting light of at least one of violet,blue, and blue green, and wherein the second light-emitting layercomprises a second light-emitting substance emitting light of at leastone of green, yellow green, yellow, orange, and red.
 3. Thelight-emitting device according to claim 1, further comprising a firstreflective electrode in contact with the first transparent conductivefilm, wherein an optical path length between the first reflectiveelectrode and the first light-emitting layer is greater than or equal to¾λ_(B), λ_(B) being a wavelength range of greater than or equal to 420nm and less than or equal to 480 nm, and wherein the first reflectiveelectrode comprises silver.
 4. The light-emitting device according toclaim 1, further comprising: a second reflective electrode in contactwith the second transparent conductive film; and a third reflectiveelectrode in contact with the third transparent conductive film, whereinan optical path length between the second reflective electrode and thefirst light-emitting layer is less than ¾λ_(G), λ_(G) being a wavelengthrange of greater than or equal to 500 nm and less than 550 nm, whereinan optical path length between the third reflective electrode and thefirst light-emitting layer is less than ¾λ_(R), λ_(R) being a wavelengthrange of greater than or equal to 600 nm and less than or equal to 740nm, wherein the second reflective electrode comprises silver, andwherein the third reflective electrode comprises silver.
 5. Thelight-emitting device according to claim 1, further comprising: a secondreflective electrode in contact with the second transparent conductivefilm; and a third reflective electrode in contact with the thirdtransparent conductive film, wherein an optical path length between thesecond reflective electrode and the second light-emitting layer isaround ¾λ_(G), λ_(G) being a wavelength range of greater than or equalto 500 nm and less than 550 nm, wherein an optical path length betweenthe third reflective electrode and the second light-emitting layer isaround ¾λ_(R), λ_(R) being a wavelength range of greater than or equalto 600 nm and less than or equal to 740 nm, wherein the secondreflective electrode comprises silver, and wherein the third reflectiveelectrode comprises silver.
 6. An electronic device comprising: thelight-emitting device according to claim 1, and at least one of ahousing and a touch sensor.
 7. A light-emitting device comprising: afirst light-emitting element being capable of emitting blue light, thefirst light-emitting element comprising: a first transparent conductivefilm; a first light-emitting layer over the first transparent conductivefilm; a second light-emitting layer over the first light-emitting layer;and an electrode over the second light-emitting layer, a secondlight-emitting element being capable of emitting green light, the secondlight-emitting element comprising: a second transparent conductive film;the first light-emitting layer over the second transparent conductivefilm; the second light-emitting layer over the first light-emittinglayer; and the electrode over the second light-emitting layer, a thirdlight-emitting element being capable of emitting red light, the thirdlight-emitting element comprising: a third transparent conductive film;the first light-emitting layer over the third transparent conductivefilm; the second light-emitting layer over the first light-emittinglayer; and the electrode over the second light-emitting layer, and afourth light-emitting element being capable of emitting white light, thefourth light-emitting element comprising: a fourth transparentconductive film; the first light-emitting layer over the fourthtransparent conductive film; the second light-emitting layer over thefirst light-emitting layer; and the electrode over the secondlight-emitting layer, wherein the first transparent conductive film hasa first region, wherein the second transparent conductive film has asecond region, wherein the third transparent conductive film has a thirdregion, wherein the fourth transparent conductive film has a fourthregion, wherein the first region is thicker than the third region andthe fourth region, wherein each of the third region and the fourthregion is thicker than the second region, wherein the firstlight-emitting layer comprises a fluorescent compound, and wherein thesecond light-emitting layer comprises a phosphorescent compound.
 8. Thelight-emitting device according to claim 7, wherein the firstlight-emitting layer comprises a first light-emitting substance emittinglight of at least one of violet, blue, and blue green, and wherein thesecond light-emitting layer comprises a second light-emitting substanceemitting light of at least one of green, yellow green, yellow, orange,and red.
 9. The light-emitting device according to claim 7, furthercomprising a first reflective electrode in contact with the firsttransparent conductive film, wherein an optical path length between thefirst reflective electrode and the first light-emitting layer is greaterthan or equal to ¾λ_(B), λ_(B) being a wavelength range of greater thanor equal to 420 nm and less than or equal to 480 nm, and wherein thefirst reflective electrode comprises silver.
 10. The light-emittingdevice according to claim 7, further comprising: a second reflectiveelectrode in contact with the second transparent conductive film; and athird reflective electrode in contact with the third transparentconductive film, wherein an optical path length between the secondreflective electrode and the first light-emitting layer is less than¾λ_(G), λ_(G) being a wavelength range of greater than or equal to 500nm and less than 550 nm, wherein an optical path length between thethird reflective electrode and the first light-emitting layer is lessthan ¾λ_(R), λ_(R) being a wavelength range of greater than or equal to600 nm and less than or equal to 740 nm, wherein the second reflectiveelectrode comprises silver, and wherein the third reflective electrodecomprises silver.
 11. The light-emitting device according to claim 7,further comprising: a second reflective electrode in contact with thesecond transparent conductive film; and a third reflective electrode incontact with the third transparent conductive film, wherein an opticalpath length between the second reflective electrode and the secondlight-emitting layer is around ¾λ_(G), λ_(G) being a wavelength range ofgreater than or equal to 500 nm and less than 550 nm, wherein an opticalpath length between the third reflective electrode and the secondlight-emitting layer is around ¾λ_(R), λ_(R) being a wavelength range ofgreater than or equal to 600 nm and less than or equal to 740 nm,wherein the second reflective electrode comprises silver, and whereinthe third reflective electrode comprises silver.
 12. An electronicdevice comprising: the light-emitting device according to claim 7, andat least one of a housing and a touch sensor.